3x(12x – 4) – 9x(4x – 3) = 30

3x.12x – 3x.4 – (9x.4x – 9x.3) = 30

36x2 – 12x – 36x2 + 27x = 30

(36x2 – 36x2) + (27x – 12x) = 30

15x = 30

x = 2

Vậy x = 2.

3x (12x -4 )- 9x (4x-3)= 30 

<=>36x²-12x-36x³+27x=30

<=>15x=30

<=>x=2

1) Ta có: \(\left(x+5\right)\left(x+2\right)-3\left(4x-3\right)=\left(5-x\right)^2\)

\(\Leftrightarrow x^2+2x+5x+10-12x+9=25-10x+x^2\)

\(\Leftrightarrow x^2-5x+19-25+10x-x^2=0\)

\(\Leftrightarrow5x-6=0\)

\(\Leftrightarrow5x=6\)

\(\Leftrightarrow x=\frac{6}{5}\)

Vậy: \(x=\frac{6}{5}\)

2) Ta có: \(\left(x+2\right)^3-\left(x-2\right)^3=12x\left(x-1\right)-8\)

\(\Leftrightarrow x^3+6x^2+12x+8-\left(x^3-6x^2+12x-8\right)=12x^2-12x-8\)

\(\Leftrightarrow x^3+6x^2+12x+8-x^3+6x^2-12x+8-12x^2+12x+8=0\)

\(\Leftrightarrow12x+24=0\)

\(\Leftrightarrow12x=-24\)

\(\Leftrightarrow x=-2\)

Vậy: x=-2

3) Ta có: \(3x\left(12x-4\right)-9x\left(4x-3\right)=30\)

\(\Leftrightarrow36x^2-12x-36x^2+27x-30=0\)

\(\Leftrightarrow15x-30=0\)

\(\Leftrightarrow15x=30\)

\(\Leftrightarrow x=2\)

Vậy: x=2

4) Ta có: \(\left(12x-5\right)\left(4x-1\right)+\left(3x-7\right)\left(1-16x\right)=81\)

\(\Leftrightarrow48x^2-12x-20x+5+3x-48x^2-7+112x-81=0\)

\(\Leftrightarrow83x-83=0\)

\(\Leftrightarrow83x=83\)

\(\Leftrightarrow x=1\)

Vậy: x=1

\(3x\left(12x-4\right)-9x\left(4x-3\right)=30\)

\(36x^2-12x-36x^2+27x=30\)

\(15x=30\)

\(x=\frac{30}{15}\)

\(x=2\)

= 36X-12X-36X-27X=30

=36X-36X-12X-27X=30

=0-12X-27X

=-12X-27X=30

=X.(-12-27)=30

hình như mình tính sai

nếu công thức đúng thì k nha

\(3x\left(12x-4\right)-9x\left(4x-3\right)=30\)

\(\Leftrightarrow15x=30\)

\(\Leftrightarrow x=2\)

3x(12x+4)-9x(4x-3)=30

=>36.x²+12x-36.x²-27x=30

=>12x-27x=30

=>-15x=30

=>x=30:(-15)

=>x=-2

vậy......

\(3x\left(12x-4\right)-9x\left(4x-3\right)=30\)

=>\(36x^2-12x-36x^2+17x=30\)

=>\(17x-12x=30\)

=>\(5x=30\)

=>x=30:5

=>x=6

\(3.\left(12x-4\right)-9.\left(4x-3\right)=30\)

\(\Rightarrow36x-12-36x+27=30\)

\(\Rightarrow36x-36x=30+12-27\)

\(\Rightarrow x.\left(36-36\right)=15\)

\(\Rightarrow x.0=15\)

\(\Rightarrow x=15:0\) \(???\)

    ĐỀ bài sai rồi 

3x.12x+3x.(-4)-9x.4x-9x.(-3)=30

36x²-12x-36x²-27x=30   

24x-9x=30

15x=30

=>x=30:15

=>x=2

3x(12x-4)-9x(4x-3)=30

3x12x+3x-4-9x4x-9x-3=30

36x^2-12x-36x^2+27x=30

(36^2-36x^2)+(-12x+27x)=30

       0         +     15x     =30

=> 15x=30

Vậy: x=30:15=2

\(3x\left(12x-4\right)-9x\left(4x-3\right)=30\)

\(36x^2-12x-36x^2+27x=30\)

\(15x=30\)

\(x=2\)

Giải:

\(3x\left(12x-4\right)-9x\left(4x-3\right)=30\)

\(\Leftrightarrow36x^2-12x-36x^2+27x=30\)

\(\Leftrightarrow-12x+27x=30\)

\(\Leftrightarrow15x=30\)

\(\Leftrightarrow x=\dfrac{30}{15}\)

\(\Leftrightarrow x=2\)

Vậy \(x=2\).

Chúc bạn học tốt!!!

3x (12x-4) -9x( 4x-3) = 30

3x.12x- 3x.4 -9x.4x+ 9x.3= 30

36x\(^2\)-12x-36x\(^2\) +18x =30

6x = 30

=> x= 5

Chúc bạn học tốt !!

36x²-12x-36x²+27x=30

15x=30

x=2