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\(a.20-\left[30-\left(5-1\right)^2\right]\) \(b.75-\left(3.5^2-4.2^3\right)\)
\(=20-\left[30-4^2\right]\) \(=75-\left(75-4.2^3\right)\)
\(=20-14=6\) \(=75-\left(75-32\right)\)
\(=75-43=32\)
a)\(\left(-3\right).8.\left(-2\right).5=\left(-3\right).\left(-2\right).8.5\)
\(=6.40=240\)
b)\(127-18.\left(5+6\right)=127-18.11\)
\(=127-198=-71\)
c)\(125-\left(-75\right)+32-\left(48+32\right)=125+75+32-48-32\)
\(\left(125+75\right)+\left(32-32\right)-48=200-48=152\)
d)\(3.\left(-4\right).2+2.\left(-5\right)-20=-12.2+2.\left(-5\right)-20\)
\(=\left(-12-5\right).2-20=-17.2-20=-140-20=-160\)
Chúc bạn học tốt
Vì ( − 1 ) . ( − 2 ) . ( − 3 ) ... ( − 20 ) > 0 ( − 3 ) . ( − 4 ) . ( − 5 ) ... ( − 23 ) < 0 ⇒ ( − 1 ) . ( − 2 ) . ( − 3 ) ... ( − 20 ) > ( − 3 ) . ( − 4 ) . ( − 5 ) ... ( − 23 )
1) 5 + (-4) = 1
2) (-8) + 2 = -6
3) 8 + (-2) = 6
4) 11 + (-3) = 8
5) (-11) + 2 = -9
6) (-7) + 3 = -4
7) (-5) + 5 = 0
8) 11 + (-12) = -1
9) (-18) + 20 = 2
10) (15) + (-12) = 3
11) (-17) + 17 = 0
12) 16 + (-2) = 14
13) (30) + (-14) = 16
14) (-19) + 20 = 1
15) (-18) + 15 = -3
16) (10) + (-6) = 4
17) (-28) + 14 = -14
18) 15 + (-30) = -15
19) (15) + (-4) = 11
20) (-21) + 11 = -10
21) 8 + (-22) = -14
22) (-15) + 4 = -11
23) (-3) + 2 = -1
24) 17 + (-14) = 3
25) 17 + (-14) = 3
a ) 5 ^30 : ( 5^25 . 6 + 5^25 . 9 )
= 5^30 : [ 5^25 ( 6 + 9 ) ]
= 5^30 : [ 5^25 . 15 ]
= 5^30 : [ 5^25 . 5 . 3 ]
= 5^30 : [ 5^26 . 3 ]
= 5^30 : 5^26 : 3
= 5^4 : 3
b ) ( 20 . 2^4 + 12 . 2^4 - 48 . 2^2 ) : 8^2
= ( 20 . 2^4 + 12.2^4 - 12 . 2^2 . 2^2 ) : 8^2
= ( 20 . 2^4 + 12.2^4 - 12.2^4 ) : 8^2
= 20 . 2^4 : 8^2
= 5 . 2^2 . 2^4 : ( 2^3 )^2
= 5 . 2^6 : 2^6
= 5
= 625 : 3
= 625/3
Lời giải:
a.
$-18: \frac{3}{5}=-18.\frac{5}{3}=-30$
b.
$\frac{3}{4}:(-9)=\frac{3}{4}.\frac{-1}{9}=\frac{-1}{12}$
c.
$\frac{13}{20}-\frac{6}{7}: \frac{10}{21}=\frac{13}{20}-\frac{6}{7}.\frac{21}{10}$
$=\frac{13}{20}-\frac{9}{5}=\frac{13}{20}-\frac{36}{20}=\frac{-23}{20}$
d.
$\frac{-21}{5}: (\frac{7}{3}.\frac{7}{5})=\frac{-21}{5}: \frac{49}{15}$
$=\frac{-21}{5}.\frac{15}{49}=\frac{-9}{7}$
e.
$(\frac{-2}{5}+\frac{1}{4}): (1-\frac{2}{5})$
$=\frac{-3}{20}: \frac{3}{5}=\frac{-1}{4}$
\(\dfrac{5}{12}+\dfrac{-7}{12}=\dfrac{-2}{12}=\dfrac{-1}{6}\)
\(\dfrac{1}{2}+\dfrac{-2}{3}=\dfrac{3}{6}+\dfrac{-4}{6}=\dfrac{-1}{6}\)
\(\dfrac{3}{5}-\dfrac{4}{3}=\dfrac{9}{15}-\dfrac{20}{15}=\dfrac{-11}{15}\)
\(\dfrac{-15}{14}.\dfrac{21}{20}=\dfrac{-315}{280}=\dfrac{-9}{8}\)
\(\dfrac{-1}{6}\)
\(\dfrac{-1}{6}\)
\(\dfrac{-11}{15}\)
\(\dfrac{-9}{8}\)