<span> 3х^3+2х^2-21х-14=0;</span>
х^2(3х+2)-2(х+7)=0
(х^2-2)(3х+2)(х+7)=0
х^2-2=0 3х+2=0 х+7=0
х^2=2 3х=-2 х=-7
х=+корень из 2 х=-2/3
х=-корень из 2
1) <span>a1 = 4; a2 = 14.
d = a2 - a1 = 10
a5 = a1 + 4d = 4 + 40 = 44
S10 = 2a1 + d(n-1) / 2 * 10 = 8 + 10 (10-1) * 5 = 490
2) </span><span> b1=16; b2 = 8
q = b2/b1 = 0,5
b6 = b1 * q5 (степени) = 0.03125 * 16 = 0.5
S5 = b1 (qn(</span>степени) - 1) / q-1 = 16*(0.5 5(степени) -1) / 0.5 - 1 = 16*(0.03125-1) / -05 = около 31
8х" - 12х - 8х" - 16х = 84
- 28х =84
х = - 3