75
Объяснение:
x₁, x₁ + d, x₁+2d, x₁+3d ...
x₃ + x₅ = x₁+2d +x₁ +4d = 2x₁+6d = 22
x₁+3d = 11
3d = 11-x₁
d = (11-x₁)/3
x₄*x₆ = (x₁+3d)(x₁+5d) = (x₁+11-x₁)(x₁ + 5(11-x₁)/3) = 11(3x₁-5x₁+55)/3 = 55
55-2x₁ = 15
x₁ = 20
d = -3
S₆ = (2*20-3*5)*6/2 = 75
75
Объяснение:
x₁, x₁ + d, x₁+2d, x₁+3d ...
x₃ + x₅ = x₁+2d +x₁ +4d = 2x₁+6d = 22
x₁+3d = 11
3d = 11-x₁
d = (11-x₁)/3
x₄*x₆ = (x₁+3d)(x₁+5d) = (x₁+11-x₁)(x₁ + 5(11-x₁)/3) = 11(3x₁-5x₁+55)/3 = 55
55-2x₁ = 15
x₁ = 20
d = -3
S₆ = (2*20-3*5)*6/2 = 75