Question

Find and describe the error in the followig work -3(2x+3)=21 -6x+9=21 -6x=12 x=-2

Answer 1

-3(2x+3)=21 does not become -6x+9=21 because wrong foiling.

Explanation:

When you distribute -3 with 2x+3 you multiply both values by -3.

-3*2x = -6x

-3*3 = -9 <- This is where the error is. It's -9, not +9.