Tìm x ​ 2/ 3(1-4x)(x-1) + 4(3x-2)(x+3) = – 27 3/ (x+3)(x2-3x+9) – x(x-1)(x+1) = 27. 4) 6x(5x + 3) + 3x(1 – 10x) = 7

Đáp án:

 $2)
 x=0\\
3)
x=0\\
4)
 x=\dfrac{1}{3}$

Giải thích các bước giải:

 $2)
3(1-4x)(x-1)+4(3x-2)(x+3)=-27\\
\Leftrightarrow (3-12x)(x-1)+4(3x^2+9x-2x-6)=-27\\
\Leftrightarrow 3x-3-12x^2+12x+12x^2+28x-24=-27\\
\Leftrightarrow (-12x^2+12x^2)+(3x+28x+12x)+(-3-24)=-27\\
\Leftrightarrow 43x-27=-27\\
\Leftrightarrow 43x=-27+27=0\\
\Leftrightarrow x=0\\
3)
(x+3)(x^2-3x+9)-x(x-1)(x+1)=27\\
\Leftrightarrow x^3+3^3-x(x^2-1)=27\\
\Leftrightarrow x^3+27-x^3+x=27\\
\Leftrightarrow x=27-27=0\\
4)
6x(5x+3)+3x(1-10x)=7\\
\Leftrightarrow 30x^2+18x+3x-30x^2=7\\
\Leftrightarrow 21x=7\\
\Leftrightarrow x=\dfrac{1}{3}$