Question

solve by the elimination method 7a+8b=-6 , -7a+b=15

Answer 1

Elimination method

7a+8b = -6 --------> (1)

-7a+b = 15 ----------> (2)

To eliminate the a value add the equations (1) and (2).

7a+8b = -6

-7a+b = 15

__________

9b = 9

Divide to each side by 9.

9b/9 = 9/9

⇒ b = 1

Substitute the b value in (1).

7a+8*1 = -6

7a+8 = -6

Add 6 to each side.

7a+8+6 = -6+6

7a+14 = 0

Subtract 14 from each side.

7a+14-14 = 0-14

7a =-14

Divide to each side by 7.

7a/7 = -14/7

⇒ a = -2

Solution a = -2, b = 1.