a.x2+5x+4
=>x2+4x+x+4
=>x(x+4)+x+4
=>(x+4)(x+1)
b. x2-7x=6
=>x2-x-6x=6
=>x(x-1)-6(x-1)
=>(x-1)(x-6)
c.x2-6x+8
=>x2-2x-4x+8
=>x(x-2)-4(x-2)
=>(x-2)(x-4)
d.x2-10x+21
=>x2-3x-7x+21
=>x(x-3)-7(x-3)
=>(x-3)(x-7)
e.Bạn xem lại í e đi xem có đúng đề không?
g.x2+2x-15
=>x2+5x-3x-15
=>x(x+5)-3(x+5)
=>(x-5)(x-3)
h.x2-3x-28
=>x2+4x-7x-28
=>x(x+4)-7(x+4)
=>(x+4)(x-7)
Nhớ tick cho mình nhé
1, \(x^2+5x+4\)
\(=x^2+x+4x+4\)
\(=x\left(x+1\right)+4\left(x+1\right)\)
\(=\left(x+1\right).\left(x+4\right)\)
2, \(x^2-7x+6\)
\(=x^2-x-6x+6\)
\(=x\left(x-1\right)-6\left(x-1\right)\)
\(=\left(x+1\right)\left(x-6\right)\)
3, \(x^2-6x+8\)
\(=x^2-2x-4x+8\)
\(=x\left(x-2\right)-4\left(x-2\right)\)
\(=\left(x-2\right)\left(x-4\right)\)
4, \(x^2-10x+21\)
\(=x^2-3x-7x+21\)
\(=x\left(x-3\right)-7\left(x-3\right)\)
\(=\left(x-3\right)\left(x-7\right)\)
5, \(x^2-2x+8\)
\(=x^2+2x-4x+8\)
\(=x\left(x+2\right)-4\left(x-2\right)\)
\(=x\left(x+2\right)+4\left(x+2\right)\)
\(=\left(x+2\right)\left(x+4\right)\)
6, \(x^2+2x-15\)
\(=x^2+5x-3x-15\)
\(=x\left(x+5\right)-3\left(x+5\right)\)
\(=\left(x+5\right)\left(x-3\right)\)
7, \(x^2-3x-28\)
\(=x^2+4x-7x-28\)
\(=x\left(x+4\right)-7\left(x+4\right)\)
\(=\left(x+4\right)\left(x-7\right)\)
a) \(x^2+5x+4\)
\(=x^2+x+4x+4\)
\(=x\left(x+1\right)+4\left(x+1\right)\)
\(=\left(x+4\right)\left(x+1\right)\)
b) \(x^2-7x+6\)
\(=x^2-x-6x+6\)
\(=x\left(x-1\right)-6\left(x-1\right)\)
\(=\left(x-6\right)\left(x-1\right)\)
c) \(x^2-6x+8\)
\(=x^2-2x-4x+8\)
\(=x\left(x-2\right)-4\left(x-2\right)\)
\(=\left(x-4\right)\left(x-2\right)\)
d) \(x^2-10x+21\)
\(=x^2-3x-7x+21\)
\(=x\left(x-3\right)-7\left(x-3\right)\)
\(=\left(x-7\right)\left(x-3\right)\)
e) \(x^2-2x-8\)
\(=x^2-2x-4-4\)
\(=\left(x-2\right)\left(x+2\right)-2\left(x+2\right)\)
\(=\left(x-2-2\right)\left(x+2\right)=\left(x-4\right)\left(x+2\right)\)
f) \(x^2+2x-15\)
\(=x^2+5x-3x+15\)
\(=x\left(x+5\right)-3\left(x+5\right)\)
\(=\left(x-3\right)\left(x+5\right)\)
g) \(x^2-3x-28\)
\(=x^2+7x-4x-28\)
\(=x\left(x+7\right)-4\left(x+7\right)\)
\(=\left(x-4\right)\left(x+7\right)\)
