Câu hỏi của Phuc Nguyen

Question

Tìm giá trị của x

a)x2(x+2)-2x(x+1)-(x3-x+4)=0

b)(2x+1)2-(2x-3)(2x+3)=3(x+2)

✿✿❑ĐạT̐®ŋɢย❐✿✿ · Accepted Answer

a) $x^2\left(x+2\right)-2x\left(x+1\right)-\left(x^3-x+4\right)=0$

$\Leftrightarrow x^3+2x^2-2x^2-2x-x^3+x-4=0$

$\Leftrightarrow-\left(x+4\right)=0\Leftrightarrow x=-4$Câu trả lời: a) $x^2\left(x+2\right)-2x\left(x+1\right)-\left(x^3-x+4\right)=0$

$\Leftrightarrow x^3+2x^2-2x^2-2x-x^3+x-4=0$

$\Leftrightarrow-\left(x+4\right)=0\Leftrightarrow x=-4$

Vũ Minh Tuấn · Answer

b) $\left(2x+1\right)^2-\left(2x-3\right).\left(2x+3\right)=3.\left(x+2\right)$

$\Rightarrow\left(2x+1\right)^2-\left(2x-3\right).\left(2x+3\right)-3.\left(x+2\right)=0$

$\Rightarrow\left(2x\right)^2+2.2x.1+1-\left[\left(2x\right)^2-3^2\right]-\left(3x+6\right)=0$

$\Rightarrow4x^2+4x+1-\left(4x^2-9\right)-\left(3x+6\right)=0$

$\Rightarrow4x^2+4x+1-4x^2+9-3x-6=0$

$\Rightarrow1x+4=0$

$\Rightarrow1x=0-4$

$\Rightarrow1x=-4$

$\Rightarrow x=-4$

Vậy $x=-4.$

Chúc bạn học tốt!Câu trả lời: b) $\left(2x+1\right)^2-\left(2x-3\right).\left(2x+3\right)=3.\left(x+2\right)$