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[ 45+ (52 -20 ) ] .x =103 .15
=> (45+5).x=1000.15
=> 50x=15000
=> x=15000:50
=> x=300
[ 45 + (52 -20 ) ] .x =103 .15
(45 + 5) . x = 15000
50 . x = 15000
x = 15000 : 50
x = 300
a)5.(-8).2.(-3)
=[5.(-2)].[(-8).(-3)]
=-10.24
=-240
b)(45-135+72)-(45+72)
=45-135+72-45-72
=(45-45)+(72-72)-135
=0+0-135
=-135
c)3.(-5)2.2+2.(-5)-20
=3.25.2+2(-5)-20
=75.2+(-10)-20
=150+(-30)
=120
d)86.(-46)+46.27-46.41
=86.(-1).46+46.27-46.41
=-86.46+46.27-46.41
=46(-86+27-41)
=46(-100)
-4600
e)34(15-10)-15(34-10)
=34.15-34.10-15.34+15.10
=(34.15-15.34)+(15.10-34.10)
=[34(15-15)]+[10(15-34)]
=34.0+10(-9)
=0+(-90)
=-90
Bài làm
\(A=\frac{45^{10}\cdot5^{20}}{75^{15}}\)
\(A=\frac{\left(3^2\right)^{10}\cdot5^{10}\cdot5^{20}}{3^{15}\cdot\left(5^2\right)^{15}}\)
\(A=\frac{3^{20}\cdot5^{30}}{3^{15}\cdot5^{30}}\)
\(A=3^5\)
Vậy \(A=3^5\)
\(B=\frac{2^{15}\cdot5^{20}}{6^6\cdot8^3}\)
\(B=\frac{2^{15}\cdot5^{20}}{2^6\cdot3^3\cdot\left(2^3\right)^3}\)
\(B=\frac{2^{15}\cdot5^{20}}{2^{15}\cdot3^3}\)
\(B=\frac{5^{20}}{3^3}\)
Vậy \(B=\frac{5^{20}}{3^3}\)
\(\dfrac{20}{45}-\left(\dfrac{2}{3}-10\right)=\dfrac{4}{9}-\left(\dfrac{2-30}{3}\right)=\dfrac{4}{9}-\left(-\dfrac{28}{3}\right)=\dfrac{4}{9}+\dfrac{28}{3}=\dfrac{4}{9}+\dfrac{84}{9}=\dfrac{88}{9}\)
20/45-(2/3-10)
=20/45-(2/3-10/1)
=20/45-28/3=167/135