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Bài làm:
1) Ta có: \(2x^2+5xy+2y^2\)
\(=\left(2x^2+4xy\right)+\left(xy+2y^2\right)\)
\(=2x\left(x+2y\right)+y\left(x+2y\right)\)
\(=\left(2x+y\right)\left(x+2y\right)\)
2) Ta có: \(2x^2+2xy-4y^2\)
\(=\left(2x^2-2xy\right)+\left(4xy-4y^2\right)\)
\(=2x\left(x-y\right)+4y\left(x-y\right)\)
\(=2\left(x+2y\right)\left(x-y\right)\)
\(1)2x^2+5xy+2y^2=2x^2+4xy+xy+2y^2=\left(2x^2+4xy\right)+\left(xy+2y^2\right)=2x\left(x+2y\right)+y\left(x+2y\right)=\left(2x+y\right)\left(x+2y\right)\)\(2)2x^2+2xy-4y^2=2x^2+4xy-2xy-4y^2=\left(2x^2-2xy\right)+\left(4xy-4y^2\right)=2x\left(x-y\right)+4y\left(x-y\right)=\left(2x+4y\right)\left(x-y\right)\)
a) \(x^2-2x-15\)
\(\Leftrightarrow x^2-2x+1-16\)
\(\Leftrightarrow\left(x-1\right)^2-4^2\)
\(\Leftrightarrow\left(x-5\right)\left(x-3\right)\)
\(a,x^2-2x-15=\left(x^2-2x+1\right)-16.\)
\(=\left(x-1\right)^2-4^2\)
\(=\left(x-5\right)\left(x+3\right)\)
b) 2x^2 + 7x - 15
2x^2 + 10x - 3x -15
2x(x+5) - 3(x+5)
(x+5)(2x-3)
a, 5x^3y - 10x^2y^2 + 5xy^3 = 5xy. ( x^2 - 2xy + y^2) = 5xy.( x-y)^2
b, 2x^2 + 7x -15 = 2x^2 + 10X - 3x -15
= 2x( x+5) - 3( x+5)
= ( 2x-3) (x+5)
Bài làm:
Ta có: \(2x^2-3xy-2y^2\)
\(=\left(2x^2-4xy\right)+\left(xy-2y^2\right)\)
\(=2x\left(x-2y\right)+y\left(x-2y\right)\)
\(=\left(2x+y\right)\left(x-2y\right)\)
\(x^4+y^2-2x^2y+x^2+2x-2y\)
\(=\left(y^2-x^2y-xy\right)-\left(x^2y-x^4-x^3\right)+\left(xy-x^3-x^2\right)-\left(2y-2x^2-2x\right)\)
\(=y\left(y-x^2-x\right)-x^2\left(y-x^2-x\right)+x\left(y-x^2-x\right)-2\left(y-x^2-x\right)\)
\(=\left(y-x^2+x-2\right)\left(y-x^2-x\right)\)
\(2x^2+4x+2-2y^2=2.\left(x^2+2x+1-y^2\right)\)= \(2.\left(\left(x+1\right)^2-y^2\right)=2.\left(x+1+y\right)\left(x+1-y\right)\)
\(_{\left(-2\right)\left(y-x-1\right)\left(y+x+1\right)}\)
\(15x^2-7xy-2y^2=15x^2-10xy+3xy-2y^2=\left(15x^2-10xy\right)+\left(3xy-2y^2\right)\)
\(=5x\left(3x-2y\right)+y\left(3x-2y\right)=\left(5x+y\right)\left(3x-2y\right)\)