Answer
$a) y=x^2+C; b) y=x^2-x+C; c) y=x^3+x^2-x+C$
Work Step by Step
a) When $2x=(x^2)'$
This implies, $y'=2x$ and $y=x^2+C$
b) When $(2x-1)=(x^2-x)'$
This implies, $y'=2x-1$ and $y=x^2-x+C$
c) When $(3x^2+2x-1)=(x^3+x^2-x)'$
This implies, $y'=(x^2+x-x)$ and $y=(x^3+x^2-x+C)$