Question

va rog b,c si d
va multumesc mult!☺❤

Answer 1

b)    (4+8++12+...+2016)÷(2+4+6+...+1008)=
=[4·(1+2+3+...+504)]÷[2·(1+2+3+...+504)]=
={4·[(504·505)÷2]}÷[2·(504·505÷2)]=
=(4·127.260)÷(2·127.260)=
=509.040÷254.520=
=2

c)5+10+15+20+...+2015=
=5(1+2+3+4+...+403)=
=5(403·404÷2)=
=5·81.406=
=407.030

d)    25+50+75+...+2000=
=25(1+2+3+...+80)=
=25(80·81÷2)=
=25·3240=
=81.000