Question

41 Calculați :
a. ( 1+2+3+...+36 ) ÷ ( -18 ) =
b. ( -1-2-3-...-25 ) ÷ ( -26 ) =
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Answer 1

a. ( 1+2+3+...+36 ) ÷ ( -18 ) =

= (36×37 ÷ 2) ÷ (-18)

= 18×37 ÷ (-18)

= - 37

b. ( -1-2-3-...-25 ) ÷ ( -26 ) =

= - (1 + 2 + .. + 25) ÷ (-26)

= - (25×26 ÷ 2) ÷ (-26)

= 25/2

Answer 2

Răspuns:

$a)~ ( 1+2+3+...+36 ):( -18 ) =(36\cdot37:2):(-18)=18\cdot37:(-18)= \boxed{-37}$

$\it~~~$

$b)~ ( -1-2-3-...-25 ):( -26 ) = -(1+2+3+...+25):(-26)=$

$-(25\cdot 26:2):(-26) = 25\cdot 26:2:26 =\boxed{25:2 = \dfrac{25}{2}}$