<span>Ответ будет таким c =<span> 23</span></span>±<span> 0,1</span>
(3у-1)*(2у+5)/4*(3у-1)=(2у+5)/4
1)-40:(-8)=5
2)7/18
3)28:4*7=49
4)24:(160:100)=15%
10 Cos² x + 3 Cos x -1 = 0
t = Cos x, |t| ≤ 1
10t² +3t -1 = 0
D = 9 +40 = 49
t = (-3 -7)/20 = -1/2
t = (-3+7)/20 = 1/5
Cos x = -1/2
x = ± 2π/3 +2πn, n ∈ Z
Cos x = 1/5
x = ± arccos(1/5) +2πn, n ∈ Z