20x-70y+26-70y=20x-140y+26=2(10x-70y+13) братан держи
А^4-в^4-(а^2-в^2)(а^2+в^2)=
(а-в)(а+в)(а^2+в^2);
а^6-в^6=(а^2)^3-(в^2)^3=
(а^2-в^2)(а^4+а^2в^2+в^4)=
(а-в)(а+в)(а^4+а^2в^2+в^4);
(а^4)^2-(в^4)^2=(а^4-в^4)(а^4+в^4)=
(а-в)(а+в)(а^2+в^2)(а^4+в^4).
(3-4cos2a+2cos²2a-1)/(3+4cos2a+2cos²2a-1)=
=(2cos²2a-4cos2a+2)/2cos²2a+4cos2a+2)=
=2(cos²2a-2cos2a+1)/2(cos²2a+2cos2a+1)=(cos2a-1)²/(cos2²+1)²=
=(-2sin²a)²/(2cos²a)²=4sin^4a/4cos^4a=tg^4a
6a-3a^2-a^2+4a-4=-4a^2+10a-4