(y-5(y+5)-2y(3-y) 4a(a-5)-(a+3)^2 7(x-p)^2+14xp

[latex]1)(y-5)(y+5)-2y(3-y)=y ^{2} -25-6y+2y ^{2} =3y ^{2} -6y-25 \\ &\\2)4a(a-5)-(a+3) ^{2} =4a ^{2} -20a-(a ^{2} +9+6a)= \\ =4a ^{2} -20a-a ^{2} -9-6a=3a ^{2} -26a-9\\\\3)7(x-p) ^{2} +14xp=7( x^{2} +p ^{2} -2xp)+14xp= \\ =7 x^{2} +7p ^{2} -14xp+14xp=7 x^{2} +7p ^{2} [/latex]