Question

simplificando ..
a) 2(y²-2)²-(5-y²)²


b )    (5m-6)²- 18(m²-2)

Answer 1

a)
$2(y^2-2)^2-(5-y^2)^2=2(y^4-4y^2+4)-(25-10y^2+y^4)= \\ \\ 2y^4-8y^2+8-25+10y^2-y^4=\boxed{y^4+2y^2-17}$

b)
$(5m-6)^2- 18(m^2-2)=25m^2-60m+36-18m^2+36=\boxed{7m^2-60m+72}$

Answer 2

$a)\;2(y^2-2)^2-(5-y^2)^2=2(y^4-4y^2+4)-(25-10y^2+y^4)\\\\ \=2y^4-8y^2+8-25+10y^2-y^4=y^4+2y^2-17\\\\\\ b)\;(5m-6)^2-18(m^2-2)=25m^2-60m+36-18m^2-36\\\\ =7m^2-60m=7m^2-60m$