Question

calculați: S =(1+3+5+...+19)-(2+4+6+...18)

dau coroana!!!​

Answer 1

S=(1+3+5+...+19)-(2+4+6+...+18)

(1 + 2 + 3 + .... + 19 )= 19 x (1 + 19)/2 = 19 x 20/2 = 19 x10 = 190

( 2 + 4 + 6 + .... +18 ) = 18 x ( 1 + 18)/2 = 18x19/2 =18 x9,5= 171

S=190-171

S=19

Vreau coroniță,te rogg!!!