Упростите выражение: 1)2c(5c-3)-(c-2)(c-4) 2)(3a+b)(a-2b)+(2a+b)(a-5b) 3)(a-4)(a+6)+(a-10)(a-2) 4)(x+1)(x+7)-(x+2)(x+3) 5)(y-3)(5-y)-(4-y)(y+6)  

1)2c(5c-3)-(c-2)(c-4)=10c^2-6c-c^2+6c-8=9c^2-8 2)(3a+b)(a-2b)+(2a+b)(a-5b)=3a^2-5ab-2b^2+2a^2-9ab-5b^2= 5a^2-14ab-7b^2 3)(a-4)(a+6)+(a-10)(a-2)= a^2+2a-24+a^2-12a+20=2a^2-10a-4 4)(x+1)(x+7)-(x+2)(x+3)=x^2+8x+7-x^2-5x-6= 3x+1 5)(y-3)(5-y)-(4-y)(y+6)=-y^2+8y-15+y^2+2y-24=10y-39