\(x^2+10x+26+y^2+2y\)
\(=\left(x^2+10x+25\right)+\left(y^2+2y+1\right)\)
\(=\left(x+5\right)^2+\left(y+1\right)^2\)
\(\left(x+y+4\right)\left(x+y-4\right)\)
\(=\left(x+y\right)^2-16\)
\(=x^2+y^2+2xy-16\)
a, =(x^2 +10x+25) +(y^2 +2y+1)
= (x+5)^2 +(y+1)^2
b, =(x+y)^2 -4^2
= x^2 + 2xy+ y^2 -16
x2+10x+26+y2+2y=(x+5)2+(y+1)2
(x+y+4)(x+y-4)=(x+y)2-16
\(a,x^2+10x+26+y^2+2y\)
\(=x^2+10x+25+y^2+2y+1\)
\(=\left(x+5\right)^2+\left(y+1\right)^2\)
\(b,\left(x+y+4\right)\left(x+y-4\right)\)
\(=\left(x+y\right)^2-4^2\)
\(=\left(x+y\right)^2-16\)
hok tốt!
