- <u>Второй член равен среднему арифм. суммы 1 и 3</u>
![a_1=-9x^2+1; \ a_2=x+2; \ a_3=15+7x^2](https://tex.z-dn.net/?f=a_1%3D-9x%5E2%2B1%3B+%5C+a_2%3Dx%2B2%3B+%5C+a_3%3D15%2B7x%5E2)
![x+2=\frac{-9x^2+1+15+7x^2}{2}; \ x+2=\frac{-2x^2+16}{2}](https://tex.z-dn.net/?f=x%2B2%3D%5Cfrac%7B-9x%5E2%2B1%2B15%2B7x%5E2%7D%7B2%7D%3B+%5C+x%2B2%3D%5Cfrac%7B-2x%5E2%2B16%7D%7B2%7D)
![x+2=-x^2+8; \ x^2+x-6=0](https://tex.z-dn.net/?f=x%2B2%3D-x%5E2%2B8%3B+%5C+x%5E2%2Bx-6%3D0)
![x^2+x-6=0; \ \sqrt{D}=5; \ x_1=\frac{-1+5}{2}=2; \ x_2=\frac{-1-5}{2}=-3](https://tex.z-dn.net/?f=x%5E2%2Bx-6%3D0%3B+%5C+%5Csqrt%7BD%7D%3D5%3B+%5C+x_1%3D%5Cfrac%7B-1%2B5%7D%7B2%7D%3D2%3B+%5C+x_2%3D%5Cfrac%7B-1-5%7D%7B2%7D%3D-3)
x1=2
x2=-3
Х ширина
х+4 длина
х(х+4)=60
х²+4х-60=0
D=16+240=(16)²
х=(-4+16)/2=6см ширина
6+4=10см длина
Р=2(6+10)=32см
2x^2 - 4x - 14 = 0
x^2 - 2x - 7 = 0
По теореме Виета произведение корней = -7.
1
6a^2b^2*(2b-3a^3)
2
(b^2-7)*(b^2-7-b)