a)\(-25+4x^2=\left(2x-5\right)\left(2x+5\right)\)
b)\(-x^2+10x-25=-\left(x^2-10x+25\right)=-\left(x-5\right)^2\)
c)\(\frac{1}{9}x^2+\frac{2}{3}xy+y^2=\left(\frac{1}{3}x+y\right)^2\)
\(a,-25+4x^2=4x^2-25=\left(2x-5\right)\left(2x+5\right)\)
\(b,-x^2+10x-25=-\left(x^2-10x+25\right)=-\left(x-5\right)^2\)
\(c,\frac{1}{9}x^2+\frac{2}{3}xy+y^2=\left(\frac{1}{3}x\right)^2+\frac{2.1}{3}xy+y^2=\left(\frac{1}{3}x+y\right)^2\)(sửa đề)
a) \(-25+4x=\left(2x-5\right)\left(2x+5\right)\)
b) \(-x^2+10x-25=-\left(x^2-10x+25\right)=-\left(x-5\right)^2\)
c) \(\frac{1}{9}x^2+\frac{2}{3}x+y^2=\left(\frac{1}{3}x+y\right)^2\)
Good luck:3 (bài này dễ mà - _ -)