a)x2-25+y2+2xy
=(x2+2xy+y2)-25
=(x+y)2-52
=(x+y+5)(x+y-5)
b)x3+9x2-4x-36
=(x3+9x2)-(4x+36)
=x2(x+9)-4(x+9)
=(x2-4)(x+9)
=(x+2)(x-2)(x+9)
Đúng thì tick cho mình nhé !
a,\(x^2-25+y^2+2xy=\left(x^2+2xy+y^2\right)-25\)
\(=\left(x+y\right)^2-25\)
\(=\left(x+y\right)^2-5^2\)
\(=\left(x+y-5\right)\left(x+y+5\right)\)
b,\(x^3+9x^2-4x-36=\left(x^3+9x^2\right)-\left(4x+36\right)\)
\(=x^2\left(x+9\right)-4\left(x+9\right)\)
\(=\left(x^2-4\right)\left(x+9\right)\)
\(=\left(x^2-2^2\right)\left(x+9\right)\)
\(=\left(x+2\right)\left(x-2\right)\left(x+9\right)\)
