Question

1+4+7+10+...+37 va rogg​

Answer 1

Răspuns:

Explicație pas cu pas:

$1+4+7+10+...+37 = 1+(1+3)+(1+6)+(1+9)+...+(1+36) = \underbrace{1+1+1+1+...+1}_{13} + (3+6+9+...+36) = 13+3(1+2+3+...+12) = 13+3*\dfrac{12(12+1)}{2} = 13 + 3*6*13 = \bf 247$