7n : 74 = 49
5.4n + 13 = 125
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a: =34x(-100)=-3400
b: =41(-76-24)=-4100
c: =-24(125-225)=2400
d: =26(-237+137)=-2600
e: =25(-63+23)=25x(-40)=-1000
\(\left|-34\right|+(-4)\cdot(-1)^{2008}+(17-19)^2\)
\(=34+4+(-2)^2\)
\(=34+4+4\)
\(=42\)
\((-31)\cdot81-18\cdot31-31\)
\(=31\cdot(-81)-18\cdot31-31\)
\(=31\cdot(-81)-18-1\)
\(=31\cdot(-100)=-3100\)
= (25.4).[(-2). (-5)].125-(19+9).25+19.30
=100.10.125-28.25+19.30
=125000-28.5.5+19.5.6
=125000-5.(140+95)
=125000-5.235
=125000-1175
=123825
a, A = 25.(-2).4.(-5).125 - 19.25 + 9.25 + 19.30
= 125000 - 475 + 225 + 570
= 125320
@Nam Joo Hyuk
1/2×(2×x-3)+105/2=-137/2
1/2×(2×x-3)=-137/2-105/2
1/2×(2×x-3)=-242/2
2×x-3=-242/2:1/2
2×x-3=-242
2.x=(-242)+3
2.x=239
x=239:2
x=239/2
A,-12×25-25×75-25×13
=[(-12)-75-13].25
=(-100).25
-2500
B,-50/7×49/10-35/2×-10/7+ -25/3× -9/5
=(-35)-(-25)+(-13)
=-23
C,-354+265-156+125
=[(-354)-156]+(265+125)
=(-510)+277
=-233
D,-74+40-50+16-35
=(-74)+40+(-50)+16+(-35)
=[(-74)+(-35)]+[40+(-50)+16]
=(-109)+26
=-83
E,-2/3×4/5+-4/5×4/3-0,125
=-2/3.4/5+4/5.(-4/3)-0,125
=4/5.[-2/3+(-4/3)]-0,125
=4/5.(-2)-0,125
=-8/5-0,125
=(-1,6)+(-0,125)
=-1,725
\(28.76+13.28+11.28\) \(12000-\left(1500.2+1800.3+1800.2:3\right)\)
\(=28\cdot\left(76+13+11\right)\) \(=12000-9600\)
\(=28.100=2800\) \(=2400\)
Những phép sau tương tự
`125xx5+25xx74+25`
`=25xx25+25xx74+25`
`=25xx(25+74+1)`
`=25xx100`
`=2500`
a) 7n : 74 = 49
=> 7n - 4 = 49
=> 7n - 4 = 72
=> n - 4 = 2
=> n = 2 + 4
=> n = 6
b) 5.4n + 13 = 125
=> 5.4n = 125 - 13
=> 5.4n = 112
=> 4n = 112 : 5
=> 4n = 112/5
=> n \(\in\varnothing\)
\(7^n\div7^4=49\)
\(7^{n-4}=7^2\)
\(\Rightarrow n-4=2\)
\(n=2+4\)
\(n=6\)
Vậy n = 6
=))