an=a1+(n-1)б
102,8 при n=45
A) -4ab-2,5ab-a2 ;
b) 8a2+12a-2,5ab;
c) 5a-4ab-2,5ab
<span>Найдите tg(a+b) если tga и tgb корни уравнения 5х2 - 3х - 1 = 0
5x</span>² - 3x - 1 = 0
D = 9 + 4*5*1 = 29
x₁ = (3 - √29)/10
x₂ = (3 + √29)/10
tga = (3 - √29)/10
tgb = (3 + √29)/10
tg(a + b) = (tga + tgb) / (1 + tga*tgb)
tg(a + b) = [( (3 - √29)/10 + (3 + √29)/10] / [1 + (3 - √29)/10* (3 + √29)/10]
tg(a + b) =[ 6/10] / (1 - 1/5)
tg(a + b) = 3/4