Friday, August 15, 2008

Solving Equations with variables on both sides

In some equations we can see the variables on both sides. First get the variables to one side of the equation and a number on the other side of the equation.
*** Performing the same operation on both sides of an equation does not change the validity of the equation ***

Example : solve 6(b +5) = 48
Use distributive property: a ( b + c ) = a*b + a*c
6(b +5) = 48
6b + 30 = 48 (distributive property)
6b + 30 – 30 = 48 – 30 ( subtracting 30 from both sides)
6b = 18
6b / 6 = 18 / 6 (dividing both sides by 6)
b = 3

Practice:Solve
2( x + 2) = 10
3( x + 4) = 30
5(a – 2) = 0

Example : solve 4a + 3( a – 2) =1
4 a + 3 a – 6 = 1 (distributive property 3 (a – 2) = 3a – 6 )
7a – 6 = 1 ( combining like terms, 4a + 3a = 7a)
7a – 6 + 6 = 1 + 6 ( adding 6 to bothsides)
7a = 7
7a / 7 = 7 / 7 (dividing both sides by 7 )
a = 1

practice: solve
a + 2( a – 7) =1
3x + 4 ( x +2 ) = 22
7p – 3(p + 4 ) = 8


Example : solve 5x = 7 ( x -2)
5x = 7x – 14 (distributive property 7 (x – 2) = 7x – 14 )
5x – 7x = 7x - 7x - 14 (subtracting 7x from both sides to bring x terms one side)
-2x = -14
-2x / -2 = -14 /-2 ( dividing both sides by -2)
X = 7

Practice : solve
3x = 5 ( x -6)
8x = 6( x + 3)
9y = 5( y – 8)

Example: solve 2 ( x + 5 ) = 5 ( x-1)
2 x + 10 = 5x – 5 (distributive property )
2x + 10 – 10 = 5x – 5 – 10 ( subtracting 10 from both sides)
2x = 5x - 15
2x – 5x = 5x – 5x - 15 (subtracting 5x from both sides to bring x terms one side)
- 3 x = - 15
-3x / -3 = - 15 / - 3 ( dividing both sides by -3)
X = 5

Practice : solve
2 ( x - 5 ) = 6 (1- x )
5 ( y + 8 ) = 3 ( y + 20)
6 ( p – 8) = 2 ( 4- p )

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