Question

помогите,7 класс!!! даю 90 баллов​

Answer 1

$\displaystyle\bf\\1)\\\\(7-x)(2+x)+x^{2} =19\\\\14+7x-2x-x^{2} +x^{2} =19\\\\5x+14=19\\\\5x=19-14\\\\5x=5\\\\\boxed{x=1}\\\\\\-3x(2x-1)+x(6x-2)=5x+7\\\\-6x^{2} +3x+6x^{2} -2x=5x+7\\\\x=5x+7\\\\x-5x=7\\\\-4x=7\\\\\boxed{x=-1,75}\\\\2)\\\\7ay+6a=a\cdot(7y+6)\\\\15y^{2} -5y=5y\cdot 3y-5y=5y\cdot(3y-1)\\\\ma+mb+7a+7b=(ma+mb)+(7a+7b)=\\\\=m\cdot(a+b)+7\cdot(a+b)=(a+b)\cdot(m+7)\\\\x^{3} -2x^{2} -x+2=(x^{3} -2x^{2} )-(x-2)=\\\\=x^{2} \cdot(x-2)-(x-2)=(x-2)\cdot(x^{2} -1)=$

$\displaystyle\bf\\=(x-2)\cdot(x-1)\cdot(x+1)$

Answer 2

Объяснение:

1. а) (7 - х)(2 + х) + х² = 19

14 + 7х - 2х - х² + х² = 19

14 + 5х = 19

5х = 19 - 14

5х = 5

х = 1

б) -3х(2х - 1) + х(6х - 2) = 5х + 7

-6х² + 3х + 6х² - 2х = 5х + 7

х = 5х + 7

х - 5х = 7

- 4х = 7

х = - 7/4

2. а) 7ау + 6а = а • (7у + 6)

б) 15у² - 5у = 5у • (3у - 1)

в) ma + mb + 7a + 7b = m • (a + b) + 7 (a + b) = (a + b) • (m + 7)

г) х³ - 2х² - х + 2 = х² • (х - 2) - (х - 2) = (х - 2) • (х² - 1) = (х - 2) • (х - 1) • (х + 1)