7y^2+10xy-(x^2-2(-x*-5y)+25y^2)=7y^2+10xy-x^2-10xy-25y^2=-x^2-18y^2
(а^2+5(5+2а)+4(6+а))/((а+7)^2)= (а^2+25+10а+24+4а)/(а+7)^2= (а^2+2×7×а+7^2)/(а+7)^2 = (а+7)^2/(а+7)^2=1
-3(n+2)-14=-5
-3n-6-14=-5
-3n=-5+6+14
-3n=15
n=15/(-3)
n=-5
<span>x²+6x+9=0
(x+3)</span>²=0
x+3=0
x=-3
<span>3x²+2x-5=0
D=4+60=64
x1=(-2-8)/6=-5/3 u x2=(-2+8)/6=1</span>