Question

Daca A =1+2+3+....11 si B=12+13+14+...+20 atunci aflatiA+B este​

Answer 1

Răspuns:

A =1+2+3+....+11

n=11

[11×(11+1)] :2

(11×12):2

132:2

66

A=66

B=12+13+14+....+20

12=12+0×1

13=12+1×1

14=12+2×1

:

:

20=12+8×1

12×9+1×(1+2+....+8)

108+1×[8×(8+1)]:2

108+1×(8×9):2

108+1×72:2

108+72:2

108+36

144

B=144

A+B=66+144

A+B=210