(3-m)²-(m-6)*m=9-6m+m²-m²+6m=9
ОДЗ : x-9≠0
x≠9
х²-81 = (x-9)(x+9)
![\frac{(x - 9)(x + 9)}{x - 9} = x + 9 \\ x + 9 = 2x \\ x = 9](https://tex.z-dn.net/?f=%20%5Cfrac%7B%28x%20-%209%29%28x%20%2B%209%29%7D%7Bx%20-%209%7D%20%20%3D%20x%20%2B%209%20%5C%5C%20x%20%2B%209%20%3D%202x%20%5C%5C%20x%20%3D%209)
Но так как х≠9 , корней нет
a₁ = - 6,5 a₂ = - 6 Sₙ = - 42,5 n = ?
a₂ = a₁ + d
d = a₂ - a₁ = - 6 - (- 6,5) = - 6 + 6,5 = 0,5
![S_{n}=\frac{2a_{1}+d(n-1) }{2}*n\\\\-42,5=\frac{2*(-6,5)+0,5(n-1)}{2}*n\\\\(-13+0,5n-0,5)*n=-85\\\\0,5n^{2}-13,5n+85=0\\\\n^{2}-27n+170=0\\\\D=(-27)^{2}-4*170=729-680=49=7^{2}\\\\n_{1}=\frac{27+7}{2}=17\\\\n_{2}=\frac{27-7}{2}=10](https://tex.z-dn.net/?f=S_%7Bn%7D%3D%5Cfrac%7B2a_%7B1%7D%2Bd%28n-1%29%20%7D%7B2%7D%2An%5C%5C%5C%5C-42%2C5%3D%5Cfrac%7B2%2A%28-6%2C5%29%2B0%2C5%28n-1%29%7D%7B2%7D%2An%5C%5C%5C%5C%28-13%2B0%2C5n-0%2C5%29%2An%3D-85%5C%5C%5C%5C0%2C5n%5E%7B2%7D-13%2C5n%2B85%3D0%5C%5C%5C%5Cn%5E%7B2%7D-27n%2B170%3D0%5C%5C%5C%5CD%3D%28-27%29%5E%7B2%7D-4%2A170%3D729-680%3D49%3D7%5E%7B2%7D%5C%5C%5C%5Cn_%7B1%7D%3D%5Cfrac%7B27%2B7%7D%7B2%7D%3D17%5C%5C%5C%5Cn_%7B2%7D%3D%5Cfrac%7B27-7%7D%7B2%7D%3D10)
Ответ : 10 членов
A) (c-2)(c+3)-(c-1)²=c²-2c+3c-6-c²+2c-1=3c-7
) 3(a+c)²-6ac=3(a²+2ac+c²)-6ac=3(a²+c²)
B) (p-3)(p²+3p+9)-p³=p³+3p²+9p-3p²-9p-27-p³=-27