a^2-25-2ab+b^2
= (a^2 - 2ab + b^2 ) - 5^2
= (a -b)^2 - 5^2 = ( a - b - 5 ) ( a - b + 5 )
5x^2-6xy+y^2
= (3x)^2 - 2.3x.y + y^2 - (2x)^2
= (3x - y)^2 - (2x)^2
= ( 3x - y - 2x ) ( 3x - y + 2x ) = ( x - y) ( 5x - y )
2x^3-8x^2+8x
= 2x^3 - 4x^2 - 4x^2 + 8x
= 2x^2(x - 2) - 4x(x-2)
= (2x^2 - 4x)(x-2)
= 2x(x-2)(x-2) = 2x .(x-2)^2
5x-5y-3x^2+6xy-3y^2
=5(x - y) - 3(x^2 - 2xy + y^2 )
= 5(x-y) - 3(x-y)^2 = (x-y)[ 5 - 3(x-y) ]
4x^4-9x^2
= (2x^2)^2 - (3x)^2
= (2x^2 - 3x)(2x^2 + 3x)
= x(2x - 3)x(2x + 3 ) = x^2(2x - 3)(2x + 3 )
a) \(a^2-25-2ab+b^2\)
\(=\left(a-b\right)^2-25\)
\(=\left(a-b-5\right)\left(a-b+5\right)\)
b) \(5x^2-6xy+y^2\)
\(=\left(3x\right)^2-2.3x.y+y^2-\left(2x\right)^2\)
\(=\left(3x-y\right)^2-\left(2x\right)^2\)
\(=\left(3x-y-2x\right)\left(3x-y+2x\right)\)
\(=\left(x-y\right)\left(5x-y\right)\)
c) \(2x^3-8x^2+8x\)
\(=2x^3-4x^2-4x^2+8x\)
\(=2x^2\left(x-2\right)-4x\left(x-2\right)\)
\(=2x\left(x-2\right)\left(x-2\right)\)
\(=2x\left(x-2\right)^2\)
d) \(5x-5y-3x^2+6xy-3y^2\)
\(=5\left(x-y\right)-3\left(x^2-2xy+y^2\right)\)
\(=5\left(x-y\right)-3\left(x-y\right)^2\)
\(=\left(x-y\right)\left[5-3\left(x-y\right)\right]\)
e) \(4x^4-9x^2\)
\(=\left(2x^2\right)^2-\left(3x\right)^2\)
\(=\left(2x^2-3x\right)\left(2x^2+3x\right)\)
\(=x\left(2x-3\right).x\left(2x+3\right)\)
\(=x^2\left(2x-3\right)\left(2x+3\right)\)
f) \(x^8+4\)
\(=\left(x^4\right)^2+2.x^4.2+2^2-2.x^4.2\)
\(=\left(x^4+2\right)^2-4x^4\)
\(=\left(x^4+2\right)^2-\left(2x^2\right)^2\)
\(=\left(x^4+2-2x^2\right)\left(x^4+2+2x^2\right)\)
i) \(4x^2-y^2+4x+1\)
\(=\left(2x\right)^2+2.2x+1-y^2\)
\(=\left(2x+1\right)^2-y^2\)
\(=\left(2x+1-y\right)\left(2x+1+y\right)\)
j) \(3x^2-7x+10\)
\(=3\left(x^2-\dfrac{7}{3}x+\dfrac{10}{3}\right)\)
\(=3\left(x^2-2.x.\dfrac{7}{6}+\dfrac{49}{36}-\dfrac{49}{36}+\dfrac{10}{3}\right)\)
\(=3\left[\left(x-\dfrac{7}{6}\right)^2+\dfrac{71}{36}\right]\)
g) \(x^5+x+1\)
\(=x^5+x^4+x^3-x^4-x^3-x^2+x^2+x+1\)
\(=\left(x^5+x^4+x^3\right)-\left(x^4+x^3+x^2\right)+\left(x^2+x+1\right)\)
\(=x^3\left(x^2+x+1\right)-x^2\left(x^2+x+1\right)+\left(x^2+x+1\right)\)
\(=\left(x^2+x+1\right)\left(x^3-x^2-1\right)\)
h) \(x^4+2019x^2+2018x+2019\)
\(=\left(x^4-x\right)+\left(2019x^2+2019x+2019\right)\)
\(=x\left(x^3-1\right)+2019\left(x^2+x+1\right)\)
\(=x\left(x-1\right)\left(x^2+x+1\right)+2019\left(x^2+x+1\right)\)
\(=\left(x^2+x+1\right)\left[x\left(x-1\right)+2019\right]\)
\(=\left(x^2+x+1\right)\left(x^2-x+2019\right)\)
\(a^2-25-2ab+b^2=\left(a^2-2ab+b^2\right)-25=\left(a-b\right)^2-25=\left(a-b-5\right)\left(a-b+5\right)\)
\(5x^2-6xy+y^2=5x^2-5xy-xy+y^2=5x\left(x-y\right)-y\left(x-y\right)=\left(x-y\right)\left(5x-y\right)\)