Question

What is the error in the student work below?

Answer 1

This is +16x not minus 16x as shown in the problem

Explanation:

4x^3 + 4x^2 -8x-(8x^2 -16x+4)

Distribute the minus sign

4x^3 + 4x^2 -8x-8x^2 +16x-4

The error is here This is +16x not minus 16x as shown in the problem

4x^3 -4x^2 +8x-4

Answer 2

The negative 16 in the second line should be positive 16.

See attached picture: