Question

1. tìm x thuộc z biết \(\dfrac{x}{-12}\)=\(\dfrac{-3}{2}\)

2 tính

a,\(\dfrac{-7}{9}\times\dfrac{6}{11}+\dfrac{-2}{9}\)

b,\(\dfrac{-4}{7}:2=\)

c,115- (24-5\(\times\)3)

d,\(\dfrac{-3}{7}\times\dfrac{5}{9}+\dfrac{4}{9}\times\dfrac{-3}{7}+2\dfrac{3}{7}\)

e,\(\dfrac{1}{4\times5}+\dfrac{1}{6\times7}+......\dfrac{1}{79\times80}\)

Answer 1

1,

x =( -12 . ( -3) ) : 2

x = 18

2,

a, -7/9 . 6/11 + (-2/9) = -14/33 + (-2/9) = -64/99

b, -4/7 : 2 = -4/7 . 1/2 = -2/7

c, 115 - (24 - 5. 3) = 115 - ( 24 - 15) = 115 - 9 = 106

d,= -3/7. (5/9 + 4/9) + 17/7 = -3/7 . 1 +17/7 = -3/7 . 17/7 = -51/49

e, ??? mình cx k biết

Answer 2

Lời giải:

\(\dfrac{x}{-12}=\dfrac{-3}{2}\)

\(\Rightarrow2x=-12.\left(-3\right)\)

\(\Rightarrow2x=36\)

\(\Rightarrow x=18\)