Tính:
a) | 242 | + | -300 | - | -100 |
b) ( | 15 | : | -3 | ) - | -3 |
c) ( | -1512 | : | -42 ) : | -9 |
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a) \(C_7^2 = \frac{{7!}}{{2!.5!}} = \frac{{7.6}}{2} = 21\)
b) \(C_9^0 + C_9^9 = \frac{{9!}}{{0!.9!}} + \frac{{9!}}{{9!.0!}} = 2\)
c) \(C_{15}^3 - C_{14}^3 = \frac{{15!}}{{3!.12!}} - \frac{{14!}}{{3!.11!}} = \frac{{15.14.13}}{{3.2.1}} - \frac{{14.13.12}}{{3.2.1}} = 91\)
26,72 + \(\frac{13}{100}\) + \(\frac{21}{40}\)
= 26,72 + 0,13 + 0,525
= 26,85 + 0,525
= 27,375
\(\frac{1}{4}+\frac{17}{50}+\frac{31}{100}\)
= 0,25 + 0,34 + 0,31
= 0,59 + 0,31
= 0,9
\(\frac{3}{4}+\frac{15}{40}+\frac{69}{300}\)
= 0,75 + 0,375 + 0,23
= 1,125 + 0,23
= 1,355
\(\frac{42}{700}+\frac{42}{120}+\frac{17}{80}\)
= 0,06 + 0,35 + 0,2125
= 0,41 + 0,2125
= 0,6225
a: \(=\dfrac{6}{7}\cdot\dfrac{-3}{5}=\dfrac{-18}{35}\)
b: \(=\dfrac{2}{5}\cdot\dfrac{-15}{8}=\dfrac{-30}{40}=-\dfrac{3}{4}\)
c: \(=\dfrac{2}{4}\cdot\dfrac{7}{3}=\dfrac{1}{2}\cdot\dfrac{7}{3}=\dfrac{7}{6}\)
d: \(=\dfrac{8}{3}\cdot\dfrac{16}{4}=\dfrac{128}{12}=\dfrac{32}{3}\)
Tính:
a, 8.( -9/12 )
b, ( -14/5 ) . (-10)
c, 9. ( 4/-3 )
d, -15. ( -5/6 )
e, 13. ( -2/7 )
f, 7/26. ( -13 )
\(a,8.\left(\dfrac{-9}{12}\right)=\dfrac{8.\left(-9\right)}{12}=\dfrac{-72}{12}=-6\\ b,\left(\dfrac{-14}{5}\right).\left(-10\right)=\dfrac{\left(-14\right).\left(-10\right)}{5}=\dfrac{140}{5}=28\\ c,9.\left(\dfrac{4}{-3}\right)=\dfrac{9.\left(-4\right)}{3}=\dfrac{-36}{3}=-12\\ d,-15.\left(\dfrac{-5}{6}\right)=\dfrac{\left(-15\right).\left(-5\right)}{6}=\dfrac{75}{6}\\ e,13.\left(\dfrac{-2}{7}\right)=\dfrac{13.\left(-2\right)}{7}=\dfrac{-26}{7}\\ f,\dfrac{7}{26}.\left(-13\right)=\dfrac{7.\left(-13\right)}{26}=\dfrac{-91}{26}\)
a, 8.( -9/12 )=-6
b, ( -14/5 ) . (-10)=28
c, 9. ( 4/-3 )=-12
d, -15. ( -5/6 )=25/2
e, 13. ( -2/7 )-36/7
f, 7/26. ( -13 )=-7/2
a) 442
b) 2
c) đề sai