Question

find the sum of 1+(1+2)+(1+2+3)+ to nth term​

Answer 1

Step-by-step explanation:

1+(1+2) +(1+2+3)+(1+2+3+4)+(1+2+3+4+5)+(1+2+3+4+5+6)+(1+2+3+4+5+6+7)+(1+2+3+4+5+6+7+8)+(1+2+3+4+5+6+7+8+9)

1+3+610+15+21+28+36+45

=144