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a. 15 . 23 + 4 . 32 - 5 . 7
=15 . 8+4 . 9 - 5 . 7
= 120 + 36 - 35
= 120+1
= 121
Bài 1:
\(a,\left(\frac{1}{2}\right)^{3x-1}=\frac{1}{32}\)
\(\Rightarrow\left(\frac{1}{2}\right)^{3x-1}=\left(\frac{1}{2}\right)^5\)
\(\Rightarrow3x-1=5\)
\(\Rightarrow3x=6\)
\(\Rightarrow x=2\)
\(b,\frac{64}{\left(-2\right)^x}=-8\)
\(\Rightarrow\left(-2\right)^x=64:\left(-8\right)\)
\(\Rightarrow\left(-2\right)^x=-8\)
\(\Rightarrow\left(-2\right)^x=\left(-2\right)^3\)
\(\Rightarrow x=3\)
\(c,\left(-2\right)^3+0,5x=1,5\)
\(\Rightarrow-8+0,5x=1,5\)
\(\Rightarrow0,5x=9,5\)
\(\Rightarrow x=19\)
Bài 2,
\(a,\frac{3}{8}.27\frac{1}{5}-51\frac{1}{5}.\frac{3}{8}+19=\frac{3}{8}\left(27\frac{1}{5}-51\frac{1}{5}\right)+19\)
\(=\frac{3}{8}\left(-24\right)+19\)
\(=-9+19=10\)
\(b,25\left(-\frac{1}{5}\right)^3+\frac{1}{5}-2.\left(-\frac{1}{2}\right)^2-\frac{1}{2}=-\frac{1}{5}+\frac{1}{5}-\left(-\frac{1}{2}\right)-\frac{1}{2}\)
\(=0\)
\(c,35\frac{1}{6}:\left(-\frac{4}{5}\right)-45\frac{1}{6}:\left(-\frac{4}{5}\right)=-\frac{4}{5}\left(35\frac{1}{6}-45\frac{1}{6}\right)\)
\(=-\frac{4}{5}.\left(-10\right)=8\)
\(d,\left(-0,25\right).8,7.2^2=\left(-0,25\right).8,7.4\)
\(=-1.8,7=-8,7\)
\(e,13\frac{1}{3}.\frac{5}{8}-23\frac{1}{3}:\frac{8}{5}=\frac{40}{3}.\frac{5}{8}-\frac{70}{3}.\frac{5}{8}\)
\(=\frac{5}{8}\left(\frac{40}{3}-\frac{70}{3}\right)\)
\(=\frac{5}{8}.-10\)
\(=-\frac{25}{4}\)
a) 123.42 -39.33=123.16 - 39.27 = 915
b) 53 . 48 + 53 . 22 = 53 . ( 48 + 22) = 125 . 70 = 8750
c) 815 : 813 + 39 : 36 = 82 + 33 = 64 + 27 = 91
d) 53 . 49 + 53 . 51 - 128 = 53 . ( 49 + 51 ) -128 = 5300-128 = 5172
a ) 13 . 35 + 13 . 67 - 26
= 13 . ( 35 + 67 ) - 26
= 13 . 102 - 26
= 1326 - 26
= 1300
b) ( 25 .12 + 4 . 25 ) : 27
= [ 25 . ( 12 + 4 ) ] : 27
= 25 . 16 : 27
= 25 . 24 : 27
= 29 : 27
= 22 = 4
c) 23 . [ 50 - ( 17 - 54 : 33 )] + 16
= 8 . [ 50 - ( 17 - 54 : 27 )] + 16
= 8 . [ 50 - ( 17 - 2 )] + 16
= 8 . [ 50 - 15 ] + 16
= 8 . 35 + 16
= 280 + 16
= 296
K MK NHA
a)
204 - 84 : 12
= 204 - ( 84 : 12 )
= 204 - 7
= 107
b)
15 . 23 + 4 . 32 - 5 . 7
= 15 . 8 + 4 . 9 - 5 . 7
= 120 + 36 - 35
= 156 - 35
= 121
c)
56 : 53 + 23 . 22
= 5(6-3) + 2(3+2)
= 53 + 25
= 125 + 32
= 157
d) 164 . 53 + 47 . 164
= 164 . ( 53 + 47 )
= 164 . 100
= 16400
mời bạn đừng thi thì tốt hơn 
a, 56 : 53+ 32.33-34.3
= 53 + 35 - 33
= 125 + 243 - 27
= 341
b, 36 : 32 + 23.22 -33.3
= 34 + 25 - 32
= 81 + 32 - 9
= 104
c, 23.15+23.35
= 23(15 + 35)
= 8.50
= 400
\(a,5^6:5^3+3^2.3^3-3^4.3=5^3+3^5-3^5\)
\(=5^3=125\)
\(b,3^6:3^2+2^3.2^2-3^3.3=3^4+2^5-3^4\)
\(=2^5\)
\(=32\)
\(c,2^3.15+2^3.35=2^3.3.5+2^3.5.7\)
\(=2^3.5\left(3+7\right)\)
\(=2^3.5.10\)
\(=2^3.50\)
\(=8.50\)
\(=400\)