Question

tính: -2 - 4 - 6 - 8 -..........- 88 - 90 ( ai giúp sớm mình sẽ tick cho)

Answer 1

-2-4-6-8-...-88-90

=-(2+4+6+8+...+88+90)

=-2.(1+2+3+4+...+44+45)

=\(-2.\frac{45.\left(45+1\right)}{2}=-2.\frac{45.46}{2}=-1.45.46=-1.2070=-2070\)

Answer 2

\(-2.\frac{45.\left(45+1\right)}{2}=-2070\)

Answer 3

=-2-(-2)-(-2)-...-(-2)

Có:

(88-4):2+1=43(số)

-2:44=-0,045454545...