Question

Tìm x biết

a, x(x+4)+3x=x^2+3x-4

b, 3x(4-2x)+2x(3x+1)=5+2x

Answer 1

a)\(x\left(x+4\right)+3x=x^2+3x-4\)

\(\Leftrightarrow x^2+4x+3x=x^2+3x-4\)

\(\Leftrightarrow x^2+7x=x^2+3x-4\)

\(\Leftrightarrow4x=-4\Rightarrow x=-1\)

b)\(3x\left(4-2x\right)+2x\left(3x+1\right)=5+2x\)

\(\Leftrightarrow12x-6x^2+6x^2+2x=5+2x\)

\(\Leftrightarrow14x=5+2x\)

\(\Leftrightarrow12x=5\Rightarrow x=\dfrac{5}{12}\)

Answer 2

a, \(x\left(x+4\right)+3x=x^2+3x-4\)

\(\Leftrightarrow x^2+4x+3x=x^2+3x-4\)

\(\Leftrightarrow4x=-4\Leftrightarrow x=-1\)

Vậy x = -1

b, \(3x\left(4-2x\right)+2x\left(3x+1\right)=5+2x\)

\(\Leftrightarrow12x-6x^2+6x^2+2x=5+2x\)

\(\Leftrightarrow12x=5\Leftrightarrow x=\dfrac{5}{12}\)