Tìm x

Tìm x:
a) 3x^2 + 4x =2x
b) x^4 - 16x^2 = 0
c) 25x^2 - 0,64 = 0
d) x^2 + x = 6
e) x^2 - 7x = -12
f) x^3 - x^2 = -x