Question

a=1+2+3+....+100+51x101

Answer 1

1+2+3+...+n$= \frac{n(n+1)}{2}$
a=1+2+3+...+100+51x101
a=100*101/2+51*101
a=50*101+51*101
a=101(50+51)
a=101*101=101²-patrat perfect

Answer 2

A=1+2+3+....+100+51*101
A=100*(100+1):2+51*101
A=100*101:2+51*101
A=50*101+51*101
A=101(50+51)
A=101*101
A=101²=patrat perfect