Упростите выражение: a) (y+2) ^2-2 (y+1) ^2; б) 4 (2-x) ^2+5 (x-5) ^2; в) (3-5x) ^2- (3x-2) (5x+1); г) 6 (a-2) (a-3) -4 (a-3) ^2.

a) (y+2) ^2 — 2 (y+1) ^2=[ (y+1)+1 ]^2 — 2 (y+1) ^2=(y+1) ^2+2 (y+1)+1^2 — 2 (y+1) ^2=2 (y+1)+2-1 — (y+1) ^2=2 — (y+1) ^2-2 (y+1)+1)=2 — [ (y+1) -1 ]^2=2 — [ y+1-1 ]^2=2 — y ^2 б) 4 (2-x) ^2+5 (x-5) ^2=4 (2-x) ^2+5 (3+(2-x) ^2=4 (2-x) ^2+5 (3^2+2*3*(2-x)+(2-x) ^2=4 (2-x) ^2+45+30*(2-x)+5 (2-x) ^2=9 (2-x) ^2+30 (2-x)+45=(3x-11) ^2+20 в) (3-5x) ^2- (3x-2) (5x+1)=9-30x+25x^2- (15x^2+3x-10x-2)=9-30x+25x^2-15x^2+7x+2=10x^2-23x+11=x (10x-23)+11 г) 6 (a-2) (a-3) -4 (a-3) ^2=(a-3) (6 (a-2) -4 (a-3)=(a-3) (6a-12-4a+12)=(a-3) (6a-4a)=2a (a-3)