Tìm x, ta có

f) -x(2x-5)-2x(1-x)
=
15
g)
h)
3x(12x-4)-9x(4x-3)=30
(x-1)(2x+3)-15=x(2x+5)
i)
(3x3)(521x) + (7x+4)(9x - 5) = 44
j) (x + 1)(x + 2)(x + 5) = 27+ x² (x+8)