Question

Tìm x biết

a) 2x²+3.(x-1).(x+1)=5x.(x+1)

b) (8-5x) (x+2)+4(x-2)x+1+2(x-2)(x+2)=0

Answer 1

a, \(2x^2+3\left(x-1\right)\left(x+1\right)=5x\left(x+1\right)\)

\(\Rightarrow2x^2+3\left(x^2-1\right)=5x^2+5x\)

\(\Rightarrow2x^2+3x^2-3=5x^2+5x\)

\(\Rightarrow2x^2+3x^2-5x^2-5x=3\)

\(\Rightarrow-5x=3\Rightarrow x=-\dfrac{3}{5}\)

b, \(\left(8-5x\right)\left(x+2\right)+4\left(x-2\right)\left(x+1\right)+2\left(x-2\right)\left(x+2\right)=0\)

\(\Rightarrow8x+16-5x^2-10x+4\left(x^2+x-2x-2\right)+2\left(x^2-4\right)=0\)

\(\Rightarrow8x+16-5x^2-10x+4x^2-4x-8+2x^2-8=0\)

\(\Rightarrow\left(8x-10x-4x\right)+\left(16-8-8\right)+\left(-5x^2+4x^2+2x^2\right)=0\)

\(\Rightarrow-6x+x^2=0\)

\(\Rightarrow x.\left(x-6\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}x=0\\x-6=0\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x=0\\x=6\end{matrix}\right.\)

Chúc bạn học tốt!!!

Answer 2

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

Kết quả: X ∈ {(- 1/4+√23/4 I) ,(- 1/4-√23/4 I)}

Answer 3

không không tớ viết sai bạn cứ làm theo Đoàn đức hiếu