1. Tính
a) \(\dfrac{2}{3}\)-4.(\(\dfrac{1}{2}\)+\(\dfrac{3}{4}\))
b) \(\dfrac{-2}{3}\).\(\dfrac{3}{11}\)+\(\dfrac{-16}{9}\).\(\dfrac{3}{11}\)
c) \(\dfrac{11}{125}\)-\(\dfrac{17}{18}\)-\(\dfrac{5}{7}\)+\(\dfrac{4}{9}\)+\(\dfrac{17}{14}\)
Giúp mình với
a, \(\dfrac{2}{3}-4\left(\dfrac{1}{2}+\dfrac{3}{4}\right)=\dfrac{2}{3}-4.\dfrac{5}{4}=\dfrac{2}{3}-5=-\dfrac{13}{3}\)
b, \(-\dfrac{2}{3}.\dfrac{3}{11}+\dfrac{-16}{9}.\dfrac{3}{11}=\dfrac{3}{11}.\left(-\dfrac{2}{3}+\dfrac{-16}{9}\right)\)
\(=\dfrac{3}{11}.\dfrac{-22}{9}=-\dfrac{2}{3}\)
Câu c lấy máy tính tính nha!
c,
c) \(\dfrac{11}{125}-\dfrac{17}{18}-\dfrac{5}{7}+\dfrac{4}{9}+\dfrac{17}{14}\)
\(=\dfrac{11}{125}-\dfrac{17}{18}-\dfrac{10}{14}+\dfrac{8}{18}+\dfrac{17}{14}\)
\(=\dfrac{11}{125}+\left(-\dfrac{17}{18}+\dfrac{8}{18}\right)+\left(-\dfrac{10}{14}+\dfrac{17}{14}\right)\)
\(=\dfrac{11}{125}+\left(-\dfrac{9}{18}\right)+\dfrac{7}{14}\)
\(=\dfrac{11}{125}+\left(-\dfrac{1}{2}\right)+\dfrac{1}{2}\)
\(=\dfrac{11}{125}+0=\dfrac{11}{125}\)
2. Tìm x, biết
a) \(\dfrac{-1}{4}\)-\(\dfrac{3}{4}\):x =\(\dfrac{-11}{36}\)
b) \(70\): \(\dfrac{4x+720}{x}\)=\(\dfrac{1}{2}\)
Giúp mình với
a, \(-\dfrac{1}{4}-\dfrac{3}{4}:x=-\dfrac{11}{36}\)
\(\Rightarrow\dfrac{3}{4}:x=-\dfrac{1}{4}-\left(-\dfrac{11}{36}\right)=\dfrac{1}{18}\)
\(\Rightarrow x=\dfrac{3}{4}:\dfrac{1}{18}=\dfrac{27}{2}\)
b, \(70:\dfrac{4x+720}{x}=\dfrac{1}{2}\)
\(\Rightarrow\dfrac{4x+720}{x}=140\)
\(\Rightarrow4x+720=140x\Rightarrow140x-4x=720\)
\(\Rightarrow136x=720\Rightarrow x=\dfrac{90}{17}\)
Chúc bạn học tốt!!!
a)\(\dfrac{-1}{4}-\dfrac{3}{4}:x=\dfrac{-11}{36}\)
\(\dfrac{3}{4}:x=\dfrac{-1}{4}-\left(\dfrac{-11}{36}\right)=\dfrac{1}{18}\)
\(\Rightarrow x=\dfrac{3}{4}:\dfrac{1}{18}=\dfrac{27}{2}\)
b)\(70:\dfrac{4x+720}{x}=\dfrac{1}{2}\)
\(\dfrac{4x+720}{x}=70:\dfrac{1}{2}=140\)
\(\Rightarrow4x+720=140x\)
\(\Rightarrow140x-4x=720\)
\(\Rightarrow136x=720\)
\(\Rightarrow x=\dfrac{90}{17}\)
a) (1/2)3.(1/4)2
b)16: (0,125)3.512
a) \(\left(\dfrac{1}{2}\right)^3.\left(\dfrac{1}{4}\right)^2\)
\(=\dfrac{1}{8}.\dfrac{1}{16}\)
\(=\dfrac{1}{128}\)
b) \(16:\left(0,125\right)^3.512\)
\(=16:\dfrac{1}{512}.512\)
\(=16:\left(\dfrac{1}{512}.512\right)\)
\(=16:1\)
\(=16\)
a, \(\left(\dfrac{1}{2}\right)^3\). \(\left(\dfrac{1}{4}\right)^2\)
=\(\dfrac{1}{8}\).\(\dfrac{1}{16}\)
=\(\dfrac{1}{128}\)
b, 16 : (0,125)3.512
= 16 : \(\dfrac{1}{512}\).512
= 16 : 1
=16
a)\(\left(\dfrac{1}{2}\right)^3.\left(\dfrac{1}{4}\right)^2\)
=\(\dfrac{1^3}{2^3}.\dfrac{1^2}{4^2}\)
=\(\dfrac{1}{8}.\dfrac{1}{16}\)
=\(\dfrac{1}{128}\)
b)16:(0,125)3.512
=16:\(\dfrac{1}{512}\).512
=16:1
=16
Tìm x,y biết:
a)(x-3)10=(x-3)30
b)3x+2.5y=45x
c)2x-1+5.2x-2=7
Help me
Thanks
a, \(\left(x-3\right)^{10}=\left(x-3\right)^{30}\)
\(\Leftrightarrow\left(x-3\right)^{30}-\left(x-3\right)^{10}=0\)
\(\Leftrightarrow\left(x-3\right)^{10}\left[\left(x-3\right)^{20}-1\right]=0\)
\(\Leftrightarrow\left[{}\begin{matrix}\left(x-3\right)^{10}=0\\\left(x-3\right)^{20}-1=0\end{matrix}\right.\)
+) \(\left(x-3\right)^{10}=0\Leftrightarrow x=3\)
+) \(\left(x-3\right)^{20}-1=0\Leftrightarrow\left[{}\begin{matrix}x-3=1\\x-3=-1\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=4\\x=2\end{matrix}\right.\)
Vậy...
c, \(2^{x-1}+5.2^{x-2}=7\)
\(\Leftrightarrow2^{x-2}.2+5.2^{x-2}=7\)
\(\Leftrightarrow2^{x-2}\left(2+5\right)=7\)
\(\Leftrightarrow2^{x-2}=1\)
\(\Leftrightarrow x-2=0\Leftrightarrow x=2\)
Vậy x = 2
Tìm \(x\in Q\), biết rằng:
a) \(\dfrac{11}{12}-\left(\dfrac{2}{5}+x\right)=\dfrac{2}{3}\)
b) \(2x.\left(x-\dfrac{1}{7}\right)=0\)
c) \(\dfrac{3}{4}+\dfrac{1}{4}:x=\dfrac{2}{5}\)
a) \(\dfrac{11}{12}-\left(\dfrac{2}{5}+x\right)=\dfrac{2}{3}\)
\(\Leftrightarrow\dfrac{2}{5}+x=\dfrac{11}{12}-\dfrac{2}{3}\)
\(\Leftrightarrow\dfrac{2}{5}+x=\dfrac{1}{4}\)
\(\Leftrightarrow x=-\dfrac{3}{20}\in Q\) ( thỏa mãn )
Vậy x = \(-\dfrac{3}{20}\)
b) \(2x.\left(x-\dfrac{1}{7}\right)=0\)
\(\Leftrightarrow3x-2x.\dfrac{1}{7}=0\) (1)
mà \(x\in Q\) \(\Rightarrow2x.\dfrac{1}{7}\in Q\)(2)
Từ (1) và (2) \(\Rightarrow2x.\dfrac{1}{7}=0\)
\(\Rightarrow2x=\dfrac{1}{7}:0=0\)
\(\Rightarrow x=0:2=0\in Q\) (thỏa mãn)
Vậy x=0
c) \(\dfrac{3}{4}+\dfrac{1}{4}:x=\dfrac{2}{5}\)
\(\Leftrightarrow\dfrac{1}{4}:x=\dfrac{3}{4}-\dfrac{2}{5}\)
\(\Leftrightarrow\dfrac{1}{4}:x=\dfrac{7}{20}\)
\(\Leftrightarrow x=\dfrac{1}{4}:\dfrac{7}{20}\)
\(\Leftrightarrow x=\dfrac{5}{7}\in Q\)(thỏa mãn )
Vậy x= \(\dfrac{5}{7}\)
-34/37 . 74/-85
-5/9 : -7/18
= 0,8
= 1.42857142857
Máy tính cả thôi, hi hi
a) Cho x=3,7. So sánh:
A = [x] + [x+\(\dfrac{1}{5}\)] + [x+\(\dfrac{2}{5}\)] + [x+\(\dfrac{3}{5}\)] + [x+\(\dfrac{4}{5}\)] và B=[5x]
b)Tính [\(\dfrac{100}{3}\)] + [\(\dfrac{100}{3^2}\)] + [\(\dfrac{100}{3^3}\)] + [\(\dfrac{100}{3^4}\)]
c) Tính \(\left[\dfrac{50}{2}\right]+\left[\dfrac{50}{2^2}\right]+\left[\dfrac{50}{2^3}\right]+\left[\dfrac{50}{2^4}\right]+\left[\dfrac{50}{2^5}\right]\)
Cho x thuộc Q. So sánh [x] với x,so sánh [x] với y trong đó y thuộc Z, y<x
d) 723.[(−86)−4518]
Bài 13 trang 12 - sgk Toán 7 Tập 1.
d) 7/23 . [(-8/6)-45/18] = 7/23 . [(-4/3)-5/2] = 7/23 . -23/6 = -7/6
chúc bn hc tốt 
Tìm x biết:
\(\dfrac{1}{6}x+\dfrac{1}{10}x-\dfrac{4}{15}+1=0\)
\(\dfrac{1}{6}x+\dfrac{1}{10}x-\dfrac{4}{15}+1=0\Leftrightarrow\dfrac{4}{15}x=\dfrac{-11}{15}\Leftrightarrow x=\dfrac{-11}{4}\) vậy \(x=\dfrac{-11}{4}\)
