Đáp án:
a)
$6(x-3)^2+6(x+3)^2-4(x+5)(5-x)=6(x^2-6x+9)+6(x^2+6x+9)-4(25-x^2)=6x^2-36x+54+6x^2+36x+54-100+4x^2=16x^2+8$
b)
$3(x-6)^3-2(2x-1)(2x+1)(5x+2)=3(x^3-18x^2+108x-216)-2(4x^2-1)(5x+2)=3x^3-54x^2+324x-648-40x^3-16x^2+10x+4=-37x^3-70x^2+334x-644$
c)
$(x-3)^2=(x-2)(x-5)$
$x^2-6x+9=x^2-5x-2x+10$
$x=1$
d)
$(x-1)^3+(x-2)^3=x^3+(x-3)^3$
$x^3-3x^2+3x-1+x^3-6x^2+12x-8=x^3+x^3-9x^2+27x-27$
$12x=18$
$x=\dfrac{3}{2}$