Câu hỏi của Hothithuyhang

Question

Tìm x biết

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

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

Lightning Farron · Accepted Answer

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

$\Leftrightarrow12x-6x^2+6x^2+2x=5+2x$

$\Leftrightarrow14x=5+2x$

$\Leftrightarrow12x=5\Rightarrow x=\dfrac{5}{12}$Câu trả lời: 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)$3x\left(4-2x\right)+2x\left(3x+1\right)=5+2x$

$\Leftrightarrow12x-6x^2+6x^2+2x=5+2x$

$\Leftrightarrow14x=5+2x$

$\Leftrightarrow12x=5\Rightarrow x=\dfrac{5}{12}$

Nguyễn Huy Tú · Answer

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

$\Leftrightarrow12x-6x^2+6x^2+2x=5+2x$

$\Leftrightarrow12x=5\Leftrightarrow x=\dfrac{5}{12}$Câu trả lời: 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, $3x\left(4-2x\right)+2x\left(3x+1\right)=5+2x$

$\Leftrightarrow12x-6x^2+6x^2+2x=5+2x$

$\Leftrightarrow12x=5\Leftrightarrow x=\dfrac{5}{12}$

Bài 6: Giải bài toán bằng cách lập phương trình.