Question

tinh nhanh

a)7+10+13+16+...+37

b)2+3+4+...58

c)75x18+75.52+15x150

Answer 1

a)7+10+13+16+...+37

=(7+37)+(10+34)+...+(19+25)+22(4 cặp)

=44.4+22

=198

b)2+3+4+...58

=(2+58)+(3+57)+...+(29+31)+30(28 cặp)

=60+60+...+60+30

=60.28+301710

c)75x18+75.52+15x150

=75.18+75.52+15.2.75

=75(18+52+15.2)

=75.(18+52+30)

=75.100

=7500

Answer 2

a​,b, dãy số viết theo qui luật cơ bản rồi. c,75x17+75x52+15x150=75x17+75x52+30x75=75x(17+52+30)=75x99=...