Question

aratati ca nr A=(5+10+15+..........+200)/41   este patrat perfect

Answer 1

5( 1+2+3+........+40) /41 =( 5·40·41/2)÷41 = 100 = 10² =p.p.

Answer 2

[tex]A= \frac{5+10+15+..........+200}{41} \\ \\ A= \frac{5(1+2+3+...+40)}{41} \\ \\ A= \frac{5 \frac{40(40+1)}{2} }{41} \\ \\ A= \frac{5*20*41}{41} \\ \\ A=5*20 \\ \\ A=100=10^2~deci~A=p.p[/tex]