Đáp án:
Giải thích các bước giải:
a) (x-2)(x^2+2x+4)-x(x^2-3)=7
x^3-64-(x^3-3x)=7
x^3-64-x^3+3x=7
-64+3x=7
3x=7-(-64)
3x=71
x=71:3
x=71/3
b) x(x+1)^2-(x-1)^3-5x(x+2)=9
x(x^2+2x+1)-(x^3-3x^2+3x-1)-(5x^2+10x)=9
x^3+2x^2+x-x^3+3x^2-3x+1-5x^2-10x=9
-12x+1=9
-12x=8
x=-2/3
c) (x+3)^3-x(3x+1)^2+(2x+1)(4x^2-2x+1)=28
(x^3+9x^2+27x+27)-x(9x^2+6x+1)+8x^3+1=28
x^3+9x^2+27x+27-9x^3-6x^2+x+8x^3+1=28
3x^2+28x+28=28
3x^2+28x=0
=) 3x^2=0 hoặc 28x=0
=) x=0
d) (x-3)^3-(x-3)(x^2+3x+9)+6(x+1)^2+3x^2=-33
(x^3-9x^2+27x-27)-(x^3-27)+6(x^2+2x+1)+3x^2=-33
x^3-9x^2+27x-27-x^3+27+6x^2+12x+6+3x^2=-33
39x+6=-33
39x=-39
x=-1
