225а^2+60аб+4б^2-9аб+21б^2+15а^2-35аб=240а^2+16аб+25б^2=0
(5а+6)^2 -81=(5а)²+2*5а*6+6²-81=25а²+60а+36-81=25а²+60а-45
25-(а+7)^2 =25-(а²+2*а*7+7²)=25-(а²+14а+49)=25-а²-14а-49=-а²-14а-24
9m^2-(1+2m)^2=9м²-1-4м-4м²=5м²-4м-1
(5x-3y)^2 -16x^2=25х²-30ху+9у²-16х²=9х²-30ху+9у²
(5c-3d)^2 -9d^2=25с²-30сд+9д²-9д²=25с-30сд
49m^2-(n+8m)^2=49м<span>²-н²-16нм+64м²=113м²-16нм-н²</span>
y=-34.................................................
<span><span><span>х²-3х-40=0
</span></span></span>х₁+х₂=3 -- <span>теорема Виета</span>
х₁х₂= - 40
х₁=8
х₂= - 5
-y²+2y-5=-(y²-2y+4+1)=
-(y-2)²-1<0
(y-2)²>0;=>-(y-2)²<0=>(-(y-2)²-1)<0
любых значения у