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MV
9 tháng 6 2017
Gọi \(C=6,62^2+5,4\cdot3,38+1,22\cdot3,38\\ D=33,1\cdot7,1+33,1\cdot12,9\)
\(C=6,62^2+5,4\cdot3,38+1,22\cdot3,38\\ =6,62\cdot6,62+3,38\cdot\left(5,4+1,22\right)\\ =6,62\cdot6,62+3,38+6,62\\ =6,62\cdot\left(6,62+3,38\right)\\ =6,62\cdot10=66,2\)
\(D=33,1\cdot7,1+33,1\cdot12,9\\ =33,1\cdot\left(7,1+12,9\right)\\ =33,1\cdot20\\ =662\)
\(A=\dfrac{C}{D}=\dfrac{66,2}{662}=\dfrac{662}{6620}=\dfrac{1}{10}\)
\(B=A:15\%=\dfrac{1}{10}\cdot\dfrac{100}{15}=\dfrac{10}{15}\)
Vậy \(A=\dfrac{1}{10}\\ B=\dfrac{10}{15}\)
HL
Cho \(A=\frac{6,62^2+5,4.3,38+1,22.3,38}{33,1.7,1+33.1.12,9}\)
a) Rút gọn A
b) Tính B biết 15% của B=A
5
XA
3
18 tháng 8 2021
\(d,\dfrac{5}{7}+\dfrac{9}{23}+-\dfrac{12}{7}+\dfrac{14}{23}\)
\(=\left(\dfrac{5}{7}+\dfrac{-12}{7}\right)+\left(\dfrac{9}{23}+\dfrac{14}{23}\right)\)
\(=-\dfrac{7}{7}+\dfrac{23}{23}\)
\(=\left(-1\right)+1=0\)
\(e,\dfrac{3}{17}+-\dfrac{5}{13}+-\dfrac{18}{35}+\dfrac{14}{17}+\dfrac{17}{-35}+-\dfrac{8}{13}\)
\(=\left(\dfrac{3}{17}+\dfrac{14}{17}\right)+\left(\dfrac{-5}{13}+\dfrac{-8}{13}\right)+\left(\dfrac{-18}{35}+\dfrac{-17}{35}\right)\)
\(=\dfrac{17}{17}+\dfrac{-13}{13}+-\dfrac{35}{35}\)
\(=1+\left(-1\right)+\left(-1\right)=0+\left(-1\right)=-1\)
\(f,\dfrac{-3}{8}. \dfrac{1}{6}+\dfrac{3}{-8}.\dfrac{5}{6}+\dfrac{-10}{16}\)
\(=\dfrac{-3}{8}.\dfrac{1}{6}+\dfrac{-3}{8}.\dfrac{5}{6}+\dfrac{-10}{16}\)
\(=\dfrac{-3}{8}.\left(\dfrac{1}{6}+\dfrac{5}{6}\right)+-\dfrac{10}{16}\)
=\(\dfrac{-3}{8}.1+\dfrac{-10}{16}\)
\(=\dfrac{-3}{8}+\dfrac{-10}{16}\)
\(=\dfrac{-6}{16}+\dfrac{-10}{16}=\dfrac{-16}{16}=-1\)
\(g,\dfrac{-4}{11}.\dfrac{5}{15}.\dfrac{11}{-4}=\dfrac{-4}{11}.\dfrac{5}{15}.\dfrac{-11}{4}\)
\(=\left(\dfrac{-4}{11}.\dfrac{-11}{4}\right).\dfrac{5}{15}\)
\(=1.\dfrac{5}{15}=1.\dfrac{1}{3}=\dfrac{1}{3}\)
\(h,\dfrac{7}{36}-\dfrac{8}{-9}+\dfrac{-2}{3}=\dfrac{7}{36}-\dfrac{-8}{9}+\dfrac{-2}{3}\)
\(=\dfrac{7}{36}-\dfrac{-32}{36}+\dfrac{-24}{36}=\dfrac{7-\left(-32\right)+\left(-24\right)}{36}\)
\(=\dfrac{15}{56}=\dfrac{5}{12}\)
Tick mình nha ^^
18 tháng 8 2021
d.\(\dfrac{5}{7}\)+\(\dfrac{9}{23}\)+\(\dfrac{12}{7}\)+\(\dfrac{14}{23}\)=(\(\dfrac{5}{7}\)+\(\dfrac{12}{7}\))+(\(\dfrac{9}{23}\)+\(\dfrac{14}{23}\))
=\(\dfrac{17}{7}\)+ 1 = \(\dfrac{24}{7}\)
e.\(\dfrac{3}{17}\)+\(\dfrac{-5}{13}\)+\(\dfrac{-18}{35}\)+\(\dfrac{14}{17}\)+\(\dfrac{17}{-35}\)+\(\dfrac{-8}{13}\)
=(\(\dfrac{3}{17}\)+\(\dfrac{14}{17}\))+(\(\dfrac{-5}{13}\)+\(\dfrac{-8}{13}\))+(\(\dfrac{-18}{35}\)+\(\dfrac{17}{-35}\))
= 1+ (-1) + (-1) = -1
f. \(\dfrac{-3}{8}\).\(\dfrac{1}{6}\)+\(\dfrac{3}{-8}\).\(\dfrac{5}{6}\)+\(\dfrac{-10}{16}\)=\(\dfrac{-3}{8}\)(\(\dfrac{1}{6}\)+\(\dfrac{5}{6}\)) + \(\dfrac{-5}{8}\)
=\(\dfrac{-3}{8}\)+\(\dfrac{-5}{8}\)= -1
g. \(\dfrac{-4}{11}\).\(\dfrac{5}{15}\).\(\dfrac{11}{-4}\)=\(\dfrac{5}{15}\)
h.\(\dfrac{7}{36}\)-\(\dfrac{8}{-9}\)+\(\dfrac{-2}{3}\)= \(\dfrac{7}{36}\)-\(\dfrac{-32}{36}\)+\(\dfrac{-24}{36}\)
=\(\dfrac{-49}{36}\)
PN
2
14 tháng 12 2016
(x-5).(x+6)=0
suy ra: \(\hept{\begin{cases}x-5=0\Rightarrow x=5\\x+6=0\Rightarrow x=-6\end{cases}}\)
PT
1
18 tháng 8 2021
\(a,\dfrac{-3}{5}+\dfrac{7}{21}+\dfrac{-4}{5}+\dfrac{7}{5}\)
\(=\left(\dfrac{-3}{5}+\dfrac{7}{5}\right)+\dfrac{7}{21}+-\dfrac{4}{5}\)
\(=\dfrac{4}{5}+\dfrac{7}{21}+-\dfrac{4}{5}\)
\(=\left(\dfrac{4}{5}+\dfrac{-4}{5}\right)+\dfrac{7}{21}\)
\(=0+\dfrac{7}{21}=\dfrac{7}{21}\)
\(b,\dfrac{-3}{17}+\left(\dfrac{2}{3}+\dfrac{3}{17}\right)\)
\(=-\dfrac{3}{17}+\dfrac{2}{3}+\dfrac{3}{17}\)
\(=\left(\dfrac{-3}{17}+\dfrac{3}{17}\right)+\dfrac{2}{3}\)
\(=0+\dfrac{2}{3}=\dfrac{2}{3}\)
\(c,\dfrac{-5}{21}+\left(\dfrac{-16}{21}+1\right)\)
\(=\dfrac{-5}{21}+\dfrac{-16}{21}+1\)
\(=\dfrac{-21}{21}+1\)
\(=\left(-1\right)+1=0\)
Tick mình nha ^^
18 tháng 8 2021
a.\(\dfrac{-3}{5}\)+\(\dfrac{7}{21}\)+\(\dfrac{-4}{5}\)+\(\dfrac{7}{5}\)= (\(\dfrac{-3}{5}\)+\(\dfrac{-4}{5}\)+\(\dfrac{7}{5}\)) + \(\dfrac{7}{21}\)=0+\(\dfrac{7}{21}\)=\(\dfrac{7}{21}\)
b.\(\dfrac{-3}{17}\)+(\(\dfrac{2}{3}\)+\(\dfrac{3}{17}\))= \(\dfrac{-3}{17}\)+\(\dfrac{3}{17}\)+\(\dfrac{2}{3}\)=0+\(\dfrac{2}{3}\)=\(\dfrac{2}{3}\)
c.\(\dfrac{-5}{21}\)+(\(\dfrac{-16}{21}\)+1)=\(\dfrac{-5}{21}\)+\(\dfrac{-16}{21}\)+1=(-1)+ 1 = 0
CB
5
HQ
2 tháng 7 2017
2.(x - 3) = 4
x - 3 = 4 : 2
x - 3 = 2
x = 2 + 3
x = 5
kb nha !