Question

Halla “M – N” si M = 2 + 4 + 6 + 8 + ... + 40 y
N = 1 + 3 + 5 + 7 + ... + 39.

Answer 1

Aplicamos sumas notables

M = 2+4+6+8+......+2n= n(n+1)

• 2n = 40 → n = 20

Entonces:

M = 2 + 4 + 6 + 8 + ... + 40 = 20(21) = 420

____________________________

N = 1 + 3 + 5 + 7 + ... + 2n- 1 = n²

• 2n- 1 = 39 → n = 20

Entonces:

N = 1 + 3 + 5 + 7 + ... + 39 = 20² = 400

Piden " M - N"

420 - 400 = 20

Saludos