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SOLUTION OF PROBLEMS ON SIMPLE ALGEBRAIC EQUATION

Solving equation by balance method

Equation with bracket

Equation with fraction.

Solving Equation by Balance Method

To solve an equation means to find the values of the unknown in the equation that makes it true.

 

For example: 2x – 9 = 15.

2x – 9 is on the left hand side (LHS) and 15 is on the right hand side (RHS) of the equals signs.

 

Worked examples

  1. solve 3x = 12
  2. 2x – 9 = 15.

 

Solution

1.3x = 12

Divide both sides by 3

3x   = 12

3        3

x = 4.

  1. 2x – 9 = 5

add 9 to both sides since +9 is the additive inverse of (-9)

2x – 9 + 9 = 15 + 9

2x = 24

x = 24/2  = 12

 

EVALUATION

Use the balance method to solve the following

(a) 3x – 8 = 10           (b) 20 = 9x + 11          (c ) 10y – 7 = 27        (d) 9 + 2x = 16.

Equation with bracket

Worked example

  1. solve 3(3x – 1) = 4  ( x + 3)
  2. Solve 5 ( x + 11) + 2 ( 2x – 5)  = 0

Soluton

  1. 3 (3x – 1) = 4 ( x + 3)

9x  – 3  = 4x + 12

See also  LEAST COMMON MULTIPLES (LCM)

Collect like terms:

9x – 4x = 12 + 3

5x = 15

x = 15/3

x  = 3

 

  1. 5 (x + 11) + 2 ( 2x – 5)  = 0

5x + 55 + 4x – 10  = 0

collect like terms

5x + 5x = 10 – 55

9x  = -45

x = -45/9

x  = -5.

 

EVALUATION

Solve the following :

  1. 2 (x + 5) = 18 2. 6 (2s – 7)  = 5s             3.  3x + 1 = 2(3x+5)
  2. 8 (2d – 3) = 3 (4d – 7)       5. (y + 8 ) + 2 (y + 1)  = 0.

 

Equation with Fraction

Before collecting like terms in a equation always clear the fraction. To clear fraction, multiply both sides of the equation by the L.C. M. of the denominators of the fraction.

Worked examples

Solve the equations.

  1. 4m  – 2m   = 4

5         3

 

  1. 3x – 2 2x + 7     = 0

6              9

 

Solution

  1. 4m2m  = 4

5        3

LCM of 5 and 3 is 15. Multiply both sides by 15

 

15 x 4m    – 15 x 2m    = 15 x 4

5                   3

3 x 4m  – 5 x 2m  = 60

12m – 10m = 60

2m = 60

m =60

2

m = 30.

 

  1. 3x – 2 2x + 7  = 0

6             9

 

The LCM of 6 & 9 is 18. multiply both sides by 18

18  x (3x  2)   – 18 (2x + 7 )  = 0

6                        9

3(3x  2)  – 2 (2x + 7)  = 0

9x  6  – 4 x 14 = 0

See also  MASS, WEIGHT AND DENSITY

9x  4x = 14+ 6

5x = 20

x =20/5

x = 4.

 

EVALUATION

Solve the following equation

  1. 7a – 21   = 0                                2. x – 2     = 4

2                                                         3

  1. 6m  3  = 2m+ 1                           4.   –  x      = 2

7             7                                      2      3

 

WEEKEND ASSIGNMENT

  1. Solve 3x + 9 = 117

(a) 38               (b) 36    (c) -36  (d) -38

  1. If -2r = 18 what is 4?

(a) -9                (b) 20               (c) 9   (d) -20

  1. solve 2 (x + 5) = 16

(a) 13               (b) 10               (c)  8                (d) 3

  1. Solve x  = 5    (a) -15                     (b) 15     (c) 10             (d) -10

3

  1. If = ½  What is x?        (a) 2 ½                        (b) 2 2/3    (c) -2 ½        (d ) 2.

 

THEORY

  1. Solve the following (a) 4 (x + 2)  = 2 (3x – 1)    (b) 19y -2 (6y + 1)  = 8
  2. Solve the following:

(a) 5e  1/4  – 7e + 4/8    = 0

(b)  2a  1/3  – a + 5/4  = ½

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