Algebra Revision.ppt
- 2. Intermediate Tier - Algebra revision Contents : Collecting like terms Multiplying terms together Indices Expanding single brackets Expanding double brackets Substitution Solving equations Finding nth term of a sequence Simultaneous equations Inequalities Factorising – common factors Factorising – quadratics Other algebraic manipulations Solving quadratic equations Rearranging formulae Curved graphs Graphs of y = mx + c Graphing inequalities Graphing simultaneous equations Solving other equations graphically
- 3. Collecting like terms You can only add or subtract terms in an expression which have the same combination of letters in them e.g. 1. 3a + 4c + 5a + 2ac = 8a + 4c + 2ac e.g. 2. 3xy + 5yx – 2xy + yx – 3x2 = 7xy – 3x2 1. a + a + a + a + b + b + a = Simplify each of these expressions: 2. x2 + 3x – 5x + 2 = 3. ab – 5a + 2b + b2 = 4. – 9x2 + 5x – 4x2 – 9x = 5. 4a2 – 7a + 6 + 4a = 6. 4ab + 3ba – 6ba = 5a + 2b x2 – 2x + 2 cannot be simplified – 13x2 – 4x 4a2 – 3a + 6 ab
- 4. Multiplying terms together Remember your negative numbers rules for multiplying and dividing Signs same +ve answer Signs different -ve answer e.g. 1. 2 x 4a = 8a e.g. 2. - 3b x 5c = - 15bc e.g. 3. (5p)2 = 5p x 5p = 25p2 1. -6 x a = Simplify each of these expressions: 2. 4 x -3d = 3. -5a x -6c = 4. 3s x 4s = 5. a x 3a = 6. (7a)2 = -6a -12d 30ac 12s2 3a2 49a2 7. -7f x 8a = 8. 4b2 x -9 = 9. -2t x -2s = 10. 5y x 7 = 11. 6a x -a = 12. (-9k)2 = -56af -36b2 4st 35y -6a2 81k2
- 5. Indices (F2)4 t2 t2 b 1 a2 x a3 c0 a4 x7 x4 2e7 x 3ef2 4xy3 2xy 5p5qr x 6p2q6r
- 6. Expanding single brackets e.g. 4(2a + 3) = x 8a x + 12 Remember to multiply all the terms inside the bracket by the term immediately in front of the bracket If there is no term in front of the bracket, multiply by 1 or -1 Expand these brackets and simplify wherever possible: 1. 3(a - 4) = 2. 6(2c + 5) = 3. -2(d + g) = 4. c(d + 4) = 5. -5(2a - 3) = 6. a(a - 6) = 3a - 12 12c + 30 -2d - 2g cd + 4c -10a + 15 a2 - 6a 7. 4r(2r + 3) = 8. - (4a + 2) = 9. 8 - 2(t + 5) = 10. 2(2a + 4) + 4(3a + 6) = 11. 2p(3p + 2) - 5(2p - 1) = 8r2 + 12r -4a - 2 -2t - 2 16a + 32 6p2 - 6p + 5
- 7. Expanding double brackets Split the double brackets into 2 single brackets and then expand each bracket and simplify (3a + 4)(2a – 5) = 3a(2a – 5) + 4(2a – 5) = 6a2 – 15a + 8a – 20 “3a lots of 2a – 5 and 4 lots of 2a – 5” = 6a2 – 7a – 20 If a single bracket is squared (a + 5)2 change it into double brackets (a + 5)(a + 5) Expand these brackets and simplify : 1. (c + 2)(c + 6) = 2. (2a + 1)(3a – 4) = 3. (3a – 4)(5a + 7) = 4. (p + 2)(7p – 3) = c2 + 8c + 12 6a2 – 5a – 4 15a2 + a – 28 7p2 + 11p – 6 5. (c + 7)2 = 6. (4g – 1)2 = c2 + 14c + 49 16g2 – 8g + 1
- 8. Substitution If a = 5 , b = 6 and c = 2 find the value of : 3a ac 4bc a (3a)2 a2 –3b c2 (5b3 – ac)2 ab – 2c c(b – a) 4b2 Now find the value of each of these expressions if a = - 8 , b = 3.7 and c = 2/3 15 4 144 10 26 2 225 7 9.6 1 144 900
- 9. Solving equations Solve the following equation to find the value of x : 4x + 17 = 7x – 1 17 = 7x – 4x – 1 17 = 3x – 1 17 + 1 = 3x 18 = 3x 18 = x 3 6 = x x = 6 Take 4x from both sides Add 1 to both sides Divide both sides by 3 Now solve these: 1. 2x + 5 = 17 2. 5 – x = 2 3. 3x + 7 = x + 15 4. 4(x + 3) = 20 Some equations cannot be solved in this way and “Trial and Improvement” methods are required Find x to 1 d.p. if: x2 + 3x = 200 Try Calculation Comment x = 10 x = 12 (10 x 10)+(3 x 10) = 130 Too low Too high (12 x 12)+(3 x 12) = 208 etc.
- 10. Solving equations from angle problems Rule involved: Angles in a quad = 3600 4y + 2y + y + 150 = 360 7y + 150 = 360 7y = 360 – 150 7y = 210 y = 210/7 y = 300 4y 1500 y 2y Find the size of each angle Angles are: 300,600,1200,1500 Find the value of v 4v + 5 = 2v + 39 4v - 2v + 5 = 39 2v + 5 = 39 2v = 39 - 5 2v = 34 v = 34/2 v = 170 Check: (4 x 17) + 5 = 73 , (2 x 17) + 39 = 73 Rule involved: “Z” angles are equal
- 11. Finding nth term of a sequence This sequence is the 2 times table shifted a little 5 , 7 , 9 , 11 , 13 , 15 ,…….…… Position number (n) 1 2 3 4 5 6 Each term is found by the position number times 2 then add another 3. So the rule for the sequence is nth term = 2n + 3 2 4 6 8 10 12 Find the rules of these sequences 1, 3, 5, 7, 9,… 6, 8, 10, 12,……. 3, 8, 13, 18,…… 20,26,32,38,……… 7, 14, 21,28,…… 1, 4, 9, 16, 25,… 3, 6,11,18,27……. 20, 18, 16, 14,… 40,37,34,31,……… 6, 26,46,66,…… 100th term = 2 x 100 + 3 = 203 2n – 1 2n + 4 5n – 2 6n + 14 7n And these sequences n2 n2 + 2 -2n + 22 -3n + 43 20n - 14
- 12. Simultaneous equations 4a + 3b = 17 6a 2b = 6 1 Multiply the equations up until the second unknowns have the same sized number in front of them x 2 x 3 8a + 6b = 34 18a 6b = 18 2 Eliminate the second unknown by combining the 2 equations using either SSS or SDA + 26a = 52 a = 52 26 a = 2 3 Find the second unknown by substituting back into one of the equations Put a = 2 into: 4a + 3b = 17 8 + 3b = 17 3b = 17 - 8 3b = 9 b = 3 So the solutions are: a = 2 and b = 3 Now solve: 5p + 4q = 24 2p + 5q = 13
- 13. Inequalities Inequalities can be solved in exactly the same way as equations 14 2x – 8 14 + 8 2x 22 2x 11 x 22 x 2 x 11 Add 8 to both sides Divide both sides by 2 Remember to turn the sign round as well The difference is that inequalities can be given as a range of results Or on a scale: Here x can be equal to : 11, 12, 13, 14, 15, …… 8 9 10 11 12 13 14 1. 3x + 1 > 4 2. 5x – 3 12 3. 4x + 7 < x + 13 4. -6 2x + 2 < 10 Find the range of solutions for these inequalities : X > 1 X = 2, 3, 4, 5, 6 …… or X 3 X = 3, 2, 1, 0, -1 …… or X < 2 X = 1, 0, -1, -2, …… or -2 X < 4 X = -2, -1, 0, 1, 2, 3 or
- 14. Factorising – common factors Factorising is basically the reverse of expanding brackets. Instead of removing brackets you are putting them in and placing all the common factors in front. 5x2 + 10xy = 5x(x + 2y) Factorising Expanding Factorise the following (and check by expanding): 15 – 3x = 2a + 10 = ab – 5a = a2 + 6a = 8x2 – 4x = 3(5 – x) 2(a + 5) a(b – 5) a(a + 6) 4x(2x – 1) 10pq + 2p = 20xy – 16x = 24ab + 16a2 = r2 + 2 r = 3a2 – 9a3 = 2p(5q + 1) 4x(5y - 4) 8a(3b + 2a) r(r + 2) 3a2(1 – 3a)
- 15. Factorising – quadratics Here the factorising is the reverse of expanding double brackets x2 + 4x – 21 = (x + 7)(x – 3) Factorising Expanding Factorise x2 – 9x - 22 To help use a 2 x 2 box x2 - 22 x x Factor pairs of - 22: -1, 22 - 22, 1 - 2, 11 - 11, 2 Find the pair which give - 9 x2 -22 x x -11 -11x 2x 2 Answer = (x + 2)(x – 11) Factorise the following: x2 + 4x + 3 = x2 - 3x + 2 = x2 + 7x - 30 = x2 - 4x - 12 = x2 + 7x + 10 = (x + 3)(x + 1) (x – 2)(x – 1) (x + 10)(x – 3) (x + 2)(x – 6) (x + 2)(x + 5)
- 16. Fully factorise this expression: 4x2 – 25 Look for 2 square numbers separated by a minus. Simply Use the square root of each and a “+” and a “–” to get: (2x + 5)(2x – 5) Fully factorise these: (a) 81x2 – 1 (b) ¼ – t2 (c) 16y2 + 64 Answers: (a) (9x + 1)(9x – 1) (b) (½ + t)(½ – t) (c) 16(y2 + 4) Factorising a difference of two squares Other algebraic manipulations Cancelling common factors in expressions and equations These two expressions are equal: 6v2 – 9x + 27z 2v2 – 3x + 9z 3 As are these: 2(x + 3)2 2(x + 3) (x + 3) The first equation can be reduced to the second: 4x2 – 8x + 16 = 0 x2 – 2x + 4 = 0 Simplify these: (a) 5x2 + 15x – 10 = 0 (b) 4(x + 1)(x – 2) x + 1 Answers: (a) x2 + 3x – 2 = 0 (b) 4(x – 2)
- 17. Solving quadratic equations (using factorisation) Solve this equation: x2 + 5x – 14 = 0 (x + 7)(x – 2) = 0 x + 7 = 0 or x – 2 = 0 Factorise first Now make each bracket equal to zero separately 2 solutions x = - 7 or x = 2 Solve these: x2 + 4x + 4 = x2 - 7x + 10 = x2 + 12x + 35 = x2 - 5x - 6 = x2 + x - 6 = (x + 2)(x + 2) (x – 5)(x – 2) (x + 7)(x + 5) (x + 1)(x – 6) (x + 3)(x – 2) x = -2 or x = -2 x = 5 or x = 2 x = -7 or x = -5 x = -1 or x = 6 x = -3 or x = 2
- 18. Rearranging formulae a a V = u + at V V a = V - u t x t + u t - u Rearrange the following formula so that a is the subject Now rearrange these P = 4a + 5 1. A = be r 2. D = g2 + c 3. B = e + h 4. E = u - 4v d 5. 6. Q = 4cp - st Answers: 1. a = P – 5 4 2. e = Ar b 3. g = D – c 4. h = (B – e)2 5. u = d(E + 4v) 6. p = Q + st 4c
- 19. Curved graphs y x y x y x y = x2 Any curve starting with x2 is “U” shaped y = x2 3 y = x3 y = x3 + 2 Any curve starting with x3 is this shape y = 1/x y = 5/x Any curve with a number /x is this shape There are three specific types of curved graphs that you may be asked to recognise. If you are asked to draw an accurate curved graph (e.g. y = x2 + 3x – 1) simply substitute x values to find y values and thus the co-ordinates
- 20. Graphs of y = mx + c In the equation: y = mx + c m = the gradient (how far up for every one along) c = the intercept (where the line crosses the y axis) y x Y = 3x + 4 1 3 4 m c
- 21. y x Graphs of y = mx + c Write down the equations of these lines: Answers: y = x y = x + 2 y = - x + 1 y = - 2x + 2 y = 3x + 1 y = 4 y = - 3
- 22. y x x = -2 x - 2 y = x y < x y = 3 y > 3 Graphing inequalities Find the region that is not covered by these 3 regions x - 2 y x y > 3
- 23. Graphing simultaneous equations Solve these simultaneous equations using a graphical method : 2y + 6x = 12 y = 2x + 1 Finding co-ordinates for 2y + 6x = 12 using the “cover up” method: y = 0 2y + 6x = 12 x = 2 (2, 0) x = 0 2y + 6x = 12 y = 6 (0, 6) Finding co-ordinates for y = 2x + 1 x = 0 y = (2x0) + 1 y = 1 (0, 1) x = 1 y = (2x1) + 1 y = 3 (1, 3) x = 2 y = (2x2) + 1 y = 5 (2, 5) y x 2 4 6 8 -8 -6 -4 1 2 3 -4 -3 -2 -1 4 -2 2y + 6x = 12 y = 2x + 1 The co-ordinate of the point where the two graphs cross is (1, 3). Therefore, the solutions to the simultaneous equations are: x = 1 and y = 3
- 24. Solving other equations graphically If an equation equals 0 then its solutions lie at the points where the graph of the equation crosses the x-axis. e.g. Solve this equation graphically: x2 + x – 6 = 0 All you do is plot the equation y = x2 + x – 6 and find where it crosses the x-axis (the line y=0) y x 2 -3 y = x2 + x – 6 There are two solutions to x2 + x – 6 = 0 x = - 3 and x =2 Similarly to solve a cubic equation (e.g. x3 + 2x2 – 4 = 0) find where the curve y = x3 + 2x2 – 4 crosses the x-axis. These points are the solutions.