Question

Which equation is an identity?

A.3(x – 1) = x + 2(x + 1) + 1
B.x – 4(x + 1) = –3(x + 1) + 1
C.2x + 3 = 1/2 (4x + 2) + 2
D.1.3(6x – 3) = 3(x + 1) – x – 2

Answer 1

C) This one is 'funny'.

Identity means exactly the same, like 1=1.

Notice that left and right sides all have the same x! So one needs to look at the constant term:

A) -3 = 3, Nope
B) -4 = -3+1=-2, Nope
C) 3 = 1/2*2+2 =1 +2 = 3 Yup!
D) 1.3*3 = 3-2, No way!

:)