Phân tích đa thức thành nhân tử :
\(3m^2-2m-1\)
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\(\frac{2m^2+3m+1}{2m^2-m-1}=\frac{2m^2+2m+m+1}{2m^2-2m+m-1}\)
\(=\frac{2m\left(m+1\right)+\left(m+1\right)}{2m\left(m-1\right)+\left(m-1\right)}=\frac{\left(m+1\right)\left(2m+1\right)}{\left(m-1\right)\left(2m+1\right)}\)
\(=\frac{m+1}{m-1}\)
Ta có :
a3m+2a2m+am
= am(a2m+2am+1)
= am[(am)2+2am+1]
= am(am+1)2
\(=\left(m-n\right)\left(m+n\right)-2\left(m+n\right)=\left(m+n\right)\left(m-n-2\right)\)
5m^2 - 5mn + 3m - 3n
= 5m . ( m - n ) + 3 . ( m - n )
= ( m - n ) . ( 5m + 3 )
a) 9x² - 25
= (3x)² - 5²
= (3x - 5)(3x + 5)
b) y³ + 6y² + 9y
= y(y² + 6y + 9)
= y(y² + 2.y.3 + 3²)
= y(y + 3)²
c) m² - n² - 2m + 1
= (m² - 2m + 1) - n²
= (m - 1)² - n
= (m - 1 - n)(m - 1 + n)
= (m - n - 1)(m + n - 1)
Bài 2:
1) \(x^2-4x+4=\left(x-2\right)^2\)
2) \(x^2-9=x^2-3^2=\left(x-3\right)\left(x+3\right)\)
3) \(1-8x^3=\left(1-2x\right)\left(1+2x+4x^2\right)\)
4) \(\left(x-y\right)^2-9x^2=\left(x-y\right)^2-\left(3x\right)^2=\left(x-y-3x\right)\left(x-y+3x\right)=\left(-2x-y\right)\left(4x-y\right)\)
5) \(\dfrac{1}{25}x^2-64y^2=\left(\dfrac{1}{5}x-8y\right)\left(\dfrac{1}{5}x+8y\right)\)
6) \(8x^3-\dfrac{1}{8}=\left(2x-\dfrac{1}{2}\right)\left(4x^2+x+\dfrac{1}{4}\right)\)
\(3m^2-2m-1\)
\(=3m^2-3m+m-1\)
\(=3m\left(m-1\right)+\left(m-1\right)\)
\(=\left(m-1\right)\left(3m+1\right)\)
\(3m^2-2m-1\)
\(=3m^2+m-3m-1\)
\(=\left(3m^2+m\right)-\left(3m+1\right)\)
\(=m\left(3m+1\right)-\left(3m+1\right)\)
\(=\left(m-1\right)\left(3m+1\right)\)