Question

Tìm x, biết:

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

b) x(5-2x)+2x(x-1)=15

Giúp tui dzới các bác ơi.....

Answer 1

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

\(\Leftrightarrow3x\left(12x-4\right)-3x\left(12x-9\right)=30\)

\(\Leftrightarrow3x\left(12x-4-12x+9\right)=30\)

\(\Leftrightarrow3x.5=30\Leftrightarrow15x=30\)

\(\Leftrightarrow x=2\)

Vậy \(x=2\)

\(b\)) \(x\left(5-2x\right)+2x\left(x-1\right)=15\)

\(\Leftrightarrow x\left(5-2x\right)+x\left(2x-2\right)=15\)

\(\Leftrightarrow x\left(5-2x+2x-2\right)=15\)

\(\Leftrightarrow3x=15\Leftrightarrow x=5\)

Vậy \(x=5\)

Answer 2

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

<=> 36x²-12x-36x²-27x=30

<=> -12x-(-27x) =30

<=> 15x =30

<=> x = 2

b) x(5-2x)+2x(x-1)=15

<=> 5x -2x²+2x²-2x=15

<=> 5x-2x =15

<=> 3x =15

<=> x =5

Answer 3

a,3x.(12x - 4) - 9x.(4x - 3) = 30
36x^2-12x-36x^2+27x =30
15x=30
x=2

Answer 4

b.x(5-2x)+2x(x-1)=15
=> 5x - 2x^2 + 2x^2 - 2x = 15
=> 3x = 15
=> x= 15 : 3
=> x = 5