Question

Which equation is an identity?

A.8x+9=8x-3
B.7x-2=8x+4-x
C.11-(2x+3)= -2x-8
D.5x+8-x=6x-2(x-4)

Answer 1

D

Explanation:

To be an identity we require both sides of the equation to equate

A

8x + 9 ≠ 8x - 3 ← not an identity

B

7x - 2 = 8x + 4 - x = 7x + 4 ≠ 7x - 2 ← not an identity

C

11 - (2x + 3) = 11 - 2x - 3 = - 2x + 8 ≠ - 2x - 8 ← not an identity

D

5x + 8 - x = 6x - 2(x - 4), that is

4x + 8 = 6x - 2x + 8 = 4x + 8 ← both sides equate thus an identity