Ôn tập toán 7

DC

2) -12 : (\(\dfrac{3}{4}\) - \(\dfrac{5}{6}\))2

s) \(\dfrac{-1}{12}\) - (\(2\dfrac{5}{8}\) - \(\dfrac{1}{3}\))

t) -1,75 - (\(\dfrac{-1}{9}\) - \(2\dfrac{1}{18}\))

c) (\(\sqrt{\dfrac{1}{9}}\) - 0,5)3 + \(\dfrac{-1}{3}\)

d) (\(\dfrac{1}{2}\) - \(\sqrt{\dfrac{4}{25}}\))2 - \(2\dfrac{1}{2}\)

ND
25 tháng 3 2017 lúc 18:14

2) -12:\(\left(-\dfrac{5}{6}\right)^2\)=\(-12:\dfrac{25}{36}=-12\cdot\dfrac{36}{25}=-\dfrac{432}{25}\)

s) \(-\dfrac{1}{12}-\left(2\dfrac{5}{8}-\dfrac{1}{3}\right)=-\dfrac{1}{12}-\left(\dfrac{21}{8}-\dfrac{1}{3}\right)\)

= \(-\dfrac{1}{12}-\dfrac{55}{24}=-\dfrac{2}{24}-\dfrac{55}{24}=-\dfrac{57}{24}=-\dfrac{19}{8}\)

t) \(-1,75-\left(-\dfrac{1}{9}-2\dfrac{1}{18}\right)=-1,75-\left(-\dfrac{2}{18}-\dfrac{37}{18}\right)\)

= -1,75-(\(-\dfrac{13}{6}\)) = \(-\dfrac{7}{4}+\dfrac{13}{6}=\dfrac{5}{12}\)

c) \(\left(\sqrt{\dfrac{1}{9}}-0,5\right)^3+\dfrac{-1}{3}=\left(\dfrac{1}{3}-\dfrac{1}{2}\right)^3-\dfrac{1}{3}\)

= \(\left(-\dfrac{1}{6}\right)^3-\dfrac{1}{3}=\dfrac{-1}{216}-\dfrac{1}{3}=-\dfrac{73}{216}\)

d) \(\left(\dfrac{1}{2}-\sqrt{\dfrac{4}{25}}\right)^2-2\dfrac{1}{2}=\left(\dfrac{1}{2}-\dfrac{2}{5}\right)^2-\dfrac{5}{2}\)

= \(\left(\dfrac{1}{10}\right)^2-\dfrac{5}{2}=\dfrac{1}{100}-\dfrac{250}{100}=-\dfrac{249}{100}=-2,49\)

Bình luận (0)

Các câu hỏi tương tự
VK
Xem chi tiết
LD
Xem chi tiết
TC
Xem chi tiết
LD
Xem chi tiết
SK
Xem chi tiết
VT
Xem chi tiết
CT
Xem chi tiết
LD
Xem chi tiết
TQ
Xem chi tiết