phân tích thành nhân tử: x2 +2x-5
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Bài 6:
c: \(9x^2+6x+1=\left(3x+1\right)^2\)
d: \(4x^2-9=\left(2x-3\right)\left(2x+3\right)\)
e: \(x^3+27=\left(x+3\right)\left(x^2-3x+9\right)\)
b, (\(x^2\) - \(xy\) ) + (\(x-y\))
= (\(x-y\)).\(x\) + (\(x-y\))
= (\(x-y\)).(\(x\) + 1)
c, \(x^2\) - 2\(x\) - 15
= (\(x^2\) - 2\(x\) + 1) - 16
= (\(x\) - 1)2 - 42
= (\(x-1-4\)).(\(x-1+4\))
= (\(x-5\)).(\(x+3\))
1: \(\left(2x+3\right)^2-2\left(2x+3\right)\left(2x+5\right)+\left(2x+5\right)^2\)
\(=\left(2x+3-2x-5\right)^2\)
=4
\(x^2-3xy+2x-6y\)
= \(x\left(x-3y\right)+2\left(x-3y\right)\)
= \(\left(x+2\right)\left(x-3y\right)\)
= ( x2 - 4y2 ) - ( 2x + 4y )
= ( x - 2y ) ( x + 2y ) - 2 ( x - 2y )
= ( x - 2y ) ( x + 2y - 2 )
\(=\left(x-2y\right)\left(x+2y\right)-2\left(x+2y\right)=\left(x+2y\right)\left(x-2y-2\right)\)
x2 + 2x – 3
= x2 + 2x + 1 – 4
= (x + 1)2 – 22
= (x + 1 + 2)(x + 1 – 2)
= (x + 3)(x – 1)
\(x^2+2x+1-16=\left(x+1\right)^2-4^2=\left(x+1-4\right).\left(x+1+4\right)=\left(x-3\right).\left(x+5\right)\)
\(x^2+2x+1-16=\left(x^2+2x+1\right)-4^2=\left(x+1\right)^2-4^2=\left(x+1-4\right)\left(x+1+4\right)=\left(x-3\right)\left(x+5\right)\)
`x^2+2x-5`
`=(x^2+2x+1)-6`
`=(x+1)^2-\sqrt6^2`
`=(x+1+\sqrt6)(x+1-\sqrt6)`
\(x^2+2x-5\)
\(= x^2+2x+1-6\)
\(= (x+1)^2-6\)
\(= (x+1)^2-\left(\sqrt{6}\right)^2\)
\(= \left(x+1-\sqrt{6}\right)\left(x+1+\sqrt{6}\right)\)