(√50-3√2)*√2=(√2√25-3√2)*√2=√2(5-3)*√2=2*2=4
88 = (2a1 + d (n - 1) ) / 2 * n a3 + a5 = 18 a3 = a1 + 2d
88 = 8a1 + 14d 2a1 + 6d = 18 a5 = a1 + 4d
a1 = 11 - 1.75d a1 =9 - 3d
9 - 3d = 11 - 1.75d
d = - 1.6
Из первого выражения a1 = 16.1
a7 = a1 + 6d
a7 = 6.57 лет назад
А(2.5) = 0.2 - 6.25 = -6.05
f(0.5) = 2 - 0.25 = 1.75
g(0.5) = 9
f(2.5) + f(0.5)*g(0.5) = -6.05 + 1.75*9 = 9.7