Question

1 ВЫРИАНТ СРОЧНО ФОРМУЛЫ СОКРАЩЁННОГО УМНОЖЕНИЯ!!! 7 класс

Answer 1

1) (a-3)(a+5)= a²+5a-3a-15= a²+2a-15

2) (3x+1)(5+6x)= 15x+18x²+5+6x= 18x²+21x+5

3) (x³-y)(x+y)= x⁴+x³y-xy-y²

4) (a+b)(a²-4a+5b)= a³-4a²+5ab+a²b-4ab+5b²= a³-4a²+ab+a²b+5b²

5) (1-3x)(1+3x+9x²)= 1-27x³

Answer 2

$\displaystyle \tt (a-3)(a+5)=a^2+5a-3a-15=\bold{a^2+2a-15}\\\\ \displaystyle \tt (3x+1)(5+6x)=15x+18x^2+5+6x=\bold{18x^2+21x+5}\\\\ \displaystyle \tt (x^3-y)(x+y)=x^4+x^3y-xy-y^2=\bold{x^4+x^3y-y^2-xy}\\\\ \displaystyle \tt (a+b)(a^2-4a+5b)=a(a^2-4a+5b)+b(a^2-4a+5b)=\\\displaystyle \tt =a^3-4a^2+5ab+a^2b-4ab+5b^2=\bold{a^3-4a^2+ab+a^2b+5b^2}\\\\ \displaystyle \tt (1-3x)(1+3x+9x^2)=1^3-(3x)^3=\bold{1-27x^3}$