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a) (−30)+(−5)= - (30+5)= -35
b) (−7)+(−13)= -(7+13)= -20
c) (−15)+(−235)= -(15+235)= -250
a) (-30) + (-5)
= -35
b) (-7) + (-13)
= -20
c) (-15) + (-235)
= -250
Bài 4:
a; 12 - (10 - 19)
= 12 - (-9)
= 12 + 9
= 21
b; (-27) - (13 - 19)
= 27 - 16
= 11
Bài 5:
a; 321 + (-15) + 30 + (-321)
= [321 - 321] + (30 - 15)
= 0 + 15
= 15
b; 2018 + 432 + 168 + (-2018)
= [2018 - 2018] + (432 + 168)
= 0 + 600
= 600
a) \(\frac{-3}{7}.\frac{14}{15}=\frac{\left(-3\right).14}{7.15}=\frac{\left(-3\right).7.2}{7.\left(-3\right).5}=\frac{2}{5}\)
b) \(\frac{-7}{5}.\frac{15}{21}=\frac{\left(-7\right).15}{5.21}=\frac{\left(-7\right).5.3}{5.\left(-7\right).\left(-3\right)}=\frac{3}{-3}=-1\)
c) \(\frac{-9}{13}.\frac{5}{18}=\frac{\left(-9\right).5}{13.18}=\frac{\left(-9\right).5}{13.\left(-9\right).\left(-2\right)}=\frac{5}{13.\left(-2\right)}=\frac{5}{-26}\)
34 −35 +37 +311 134 −135 +137 +1311
\(=\frac{3.\left(\frac{1}{4}-\frac{1}{5}+\frac{1}{7}+\frac{1}{11}\right)}{13.\left(\frac{1}{4}-\frac{1}{5}+\frac{1}{7}+\frac{1}{11}\right)}\)
\(=\frac{3}{13}\)
Bài 2 :
Ta có:
A) | 2 + 3x | = | 4x - 3 |
<=> 2 + 3x = 4x - 3
<=> 3x - 4x = -3 - 2
=> -x = -5
=> x= 5
Mình làm có đúng ko ạ, nếu đúng thì hãy tick cho mình nhé mọi người
a)\(\frac{2}{3}+\frac{3}{4}+\frac{5}{6}\)
\(=\frac{8+9+10}{12}\)
\(=\frac{27}{12}=\frac{9}{4}\)
b)\(\frac{15}{8}-\frac{7}{12}+\frac{5}{6}\)
\(=\frac{45-14+20}{24}\)
\(=\frac{51}{24}=\frac{17}{8}\)
2)
a)\(\frac{2}{5}+\frac{7}{13}+\frac{3}{5}+\frac{1}{7}\)
\(=\frac{2}{5}+\frac{3}{5}+\frac{7}{13}+\frac{1}{7}\)
\(=1+\frac{7}{13}+\frac{1}{7}\)
\(=\frac{20}{13}+\frac{1}{7}\)
\(=\frac{153}{91}\)
Tí tớ trả lời tiếp
b)\(5\frac14+3\frac25-4\frac14\)
=\(\left(5\frac14-4\frac14\right)+3\frac25\)
=\(\left\lbrack\left(5-4\right)+\left(\frac14-\frac14\right)\right\rbrack+\frac{17}{5}\)
=\(1+0+\frac{17}{5}\)
=\(\frac55+\frac{17}{5}\)
=\(\frac{22}{5}\)
a) (–30) + (–5) = –(30 + 5) = –35.
b) (–7) + (–13) = – (7 + 13) = –20;
c) (–15) + (–235) = –(15 + 235) = –250.