Question

a)\(\)1+1+2+2+3+...+100+100=

b)       \(\frac{5}{2.3}+\frac{6}{3.4}+\frac{7}{4.5}+...+\frac{100}{97.98}=\)

Answer 1

a,1+1+2+2+3+3+...+100+100

=1x2+2x2+3x2+...+100x2

=2x(1+2+3+...+100)

=\(2.\frac{\left(100+1\right).\left[\left(100-1\right):1+1\right]}{2}\)

=2x5050

=10100

Chú ý dấu . là x

Answer 2

a, 1+1+2+2+3+...+100+100

=1+2+3+...+100+1+2+3+...+100

= (100+1)*50 /2 + (100+1)*50/2

=5050+5050

=11000