2x mũ 2 cộng 5x trừ 12
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![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(5x^3-5x^2y-10x^2+10xy=5x^2\left(x-y\right)-10x\left(x-y\right)=5x\left(x-2\right)\left(x-y\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có : \(x^4+2x^3+5x^2+4x-12=0\)
\(\Leftrightarrow x^4+2x^3+5x^2+10x-6x-12=0\)
\(\Leftrightarrow x^3\left(x+2\right)+5x\left(x+2\right)-6\left(x+2\right)=0\)
\(\Leftrightarrow\left(x+2\right)\left(x^3+5x-6\right)=0\)
\(\Leftrightarrow\left(x+2\right)\left(x^3-x^2+x^2-x+6x-6\right)=0\)
\(\Leftrightarrow\left(x+2\right)\left[x^2\left(x-1\right)+x\left(x-1\right)+6\left(x-1\right)\right]=0\)
\(\Leftrightarrow\left(x+2\right)\left(x-1\right)\left(x^2+x+6\right)=0\)
\(\Leftrightarrow\)\(x+2=0\)
hoặc \(x-1=0\)
hoặc \(x^2+x+6=0\)
\(\Leftrightarrow\) \(x=-2\)(tm)
hoặc \(x=1\)(tm)
hoặc \(\left(x+\frac{1}{2}\right)^2+\frac{23}{4}=0\)(ktm)
Vậy tập nghiệm của phương trình là \(S=\left\{-2;1\right\}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a: 3x-2=2x-3
=>x=-1
b: 2x+3=5x+9
=>-3x=6
=>x=-2
c: 5-2x=7
=>2x=-2
=>x=-2
d: 10x+3-5x=4x+12
=>5x+3=4x+12
=>x=9
e: 11x+42-2x=100-9x-22
=>9x+42=78-9x
=>18x=36
=>x=2
f: 2x-(3-5x)=4(x+3)
=>2x-3+5x=4x+12
=>7x-3=4x+12
=>3x=15
=>x=5
![](https://rs.olm.vn/images/avt/0.png?1311)
5x2 - 10xy + 5y2 - 20z2
=5(x2 - 2xy + y2 - 4z2)
= 5[ (x2 - 2xy + y2) - (2z)2]
= 5[(x-y)2 - (2z)2]
= 5(x-y-2z)(x-y+2z)
5x2-10xy+5y2-20z2
=5(x2-2xy+y2-4z2)
=5[(x-y)2-(2z)2]
=5(x-y-2z)(x-y+2z)
![](https://rs.olm.vn/images/avt/0.png?1311)
ta có :
\(x^2-5x+5y-y^2=\left(x^2-y^2\right)-5\left(x-y\right)\)
\(=\left(x-y\right)\left(x+y-5\right)\)
\(2x^2+5x-12\)
\(=2x^2+8x-3x-12\)
\(=2x\left(x+4\right)-3\left(x+4\right)\)
\(=\left(x+4\right)\left(2x-3\right)\)