Question

【高一数学】等差数列前n项的题目》》》

Answer 1

a(n) = 25 + (n-1)a,b(n) = 75 + (n-1)b,a(n)+b(n) = 100 + (n-1)(a+b),A(n)+B(n)=a(1)+b(1) + a(2)+b(2) +...+ a(n)+b(n) = 100n + n(n-1)(a+b)/2,A(100)+B(100)=100^2 + 50*99(a+b) 是 100 = a(100)+b(100)吧,100 = a(100) + b(100) = 100 + 99(a+b),99(a+b) = 0,A(100)+B(100)=100^2 + 50*99(a+b) = 100^2,选D.