25 a² + 20 ab + 4 b²
for formula \(a^x+bx^ky^k+cy ^{2k }\) find u,v such that: u.v = a
and u+v = b then group according to \((ax ^{2k} +ux^ky^k)+(vx^ky^k+cy ^{2k} )\)
= \((25a^2+10ab)+(10ab+4b^2)\)
factor out 5a from : \(25a^2+10ab : 5a(2b+5a)\)
factor out 2b from : \(10ab+4b^2: 2b(2b+5a)\)
= \(5a(2b+5a) + 2b(2b+5a)\)
factor out : \((5a+2b)\)
= \((5a+2b)(5a+2b)\)
Refine:
\((2b+5a)^2\)
hope this helps!.
