Question

tìm x

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

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

giúp mình với nha

mình rất cần

Answer 1

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

\(\Leftrightarrow8x+16-5x^2-10x+4\left(x^2-x-2\right)+2x^2-8=0\)

\(\Leftrightarrow8x+16-5x^2-10x+4x^2-4x-8+2x^2-8=0\)

\(\Leftrightarrow x^2-6x=0\)

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

Vậy pt có tập nghiệm \(S=\left\{0,6\right\}\)

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

\(\Leftrightarrow4\left(x^2+4x-5\right)-x^2-7x-10-3\left(x^2+x-2\right)=0\)

\(\Leftrightarrow4x^2+16x-20-x^2-7x-10-3x^2-3x+6=0\)

\(\Leftrightarrow6x-24=0\)

\(\Leftrightarrow x=4\)

Vậy pt có nghiệm x = 4

Answer 2

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

8x-5x²+16-10x+4(x²-2x+x-2)+2(x²-4)=0

8x-5x²+16-10x+4x²-8x+4x-8+2x²-8=0

(8-10-8+4) x+(-5+4+2)x²+(16-8-8)=0

-6x+x²=0

x(-6+x)

TH1:x=0

TH2:-6+x=0

x=6

➞KL:x∈{0;6}