a)Tìm x E N
(2x - 5 )2 - 81 =3 . 35
b)Tính
39 . (191- 113 ) - 29 . (191 - 113 )
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![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
39.(191 - 113) - 29.(191 - 113) = 39.78 - 29.78 = 78.(39 - 29) = 78.10 = 780
![](https://rs.olm.vn/images/avt/0.png?1311)
a, x - 1 2 = 36
ó x - 1 2 = 6 2
ó x – 1 = 6
ó x = 7
Vậy x = 7
b, 7 x - 11 3 = 2 5 . 5 2 + 200
=> 7 x - 11 3 = 800 + 200
=> 7 x - 11 3 = 1000
=> 7 x - 11 3 = 10 3
=> 7x – 11 = 10
=> 7x = 21
=> x = 3
Vậy x = 3
c, x 11 = x
=> x 11 - x = 0
=> x ( x 10 - 1 ) = 0
=>
d, x 2 = 2 3 + 3 2 + 4 3
=> x 2 = 81
=> x = 9
e, 2 x 3 3 2 = 48
=> 2 x 3 9 = 48
=> 2 x 3 = 48 . 9
=> x 3 = 216
=> x 3 = 6 3
=> x = 6
f, 2 x + 1 3 = 125
=> 2 x + 1 3 = 5 3
=> 2x + 1 = 5
=> 2x = 4
=> x = 2
![](https://rs.olm.vn/images/avt/0.png?1311)
a ) x = 21 55 ; b ) x = − 11 26 ; c ) x = 11 18 ; d ) x = 1
d ) x = − 1 ; e ) x = 11 7 ; f ) x = 20
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1/
a)28+2x=35-(-13)
28+2x=48
2x=48-28
x=20:2
x=10
b)2(x+1)2=-7+15
2(x+1)2=8
(x+1)2=4
x+12=22
x+1=2
x=1
c)(-25)-(x+5)=415+5(x-83)
-25-5-x=415+5x-415
-30-x=5x
-30=x+5x=6x
x=-30:6
x=-5
d)|x-2|+(-7)=-3
|x-2|=-3+7
|x-2|=4
=>x-2=4 hoặc x-2=-4
=>x=6 hoặc x=-2
Vậy x=6 hoặc x=-2
![](https://rs.olm.vn/images/avt/0.png?1311)
1.a,=(54+45+1).113
=100.113
=11300
b,=(3/7+8/14)+(4/9+10/18)
=1+1
=2
2.a,=13/10+1/3
=49/30
b,=12/9.(1/12+1/6)
=12/9.1/4
=1/3
c,=3/4.3/2
=9/8
d,=3/2-1/3
=7/6
1:tính bằng cách thuận tiện nhất:
a)54 x 113 + 45 x 113 + 113
= 54 x 113 + 45 x 113 + 113x1
=113 x(54+45+1)
= 113x100
=1300
b)3/7 + 4/9 + 8/14 + 10/18
=(3/7+8/14)+(4/9+10/18)
= 1 + 1
=2
![](https://rs.olm.vn/images/avt/0.png?1311)
c. TH1:/-8/=8
=8+(-2).3
=8-6=2
TH2:/-8/=8
=-8+(-2).3
=-8.(-6)
=-48
d.-887.(113+457)+113(887-457)
=-887.570+113.430
=-505590+48590
=-457000
e.(16+39)+(158-16-39)
=55+103
=158
c, \(\left|-8\right|+\left(-2\right).3\) => \(8+\left(-6\right)\) = \(2\)
d, \(-887.\left(113+457\right)+113.\left(887-457\right)\)
=> \(\left(-887\right).113+\left(-887\right).457+113.887-113.\left(457\right)\)
=> \(\left[\left(-887\right).113+113.887\right]+\left[\left(-887\right).457-113.457\right]\)
=> \(\left[113.\left(887-887\right)\right]+\left[457.\cdot\left(-113-887\right)\right]\)
=> \(\left[113.0\right]+\left(457.-1000\right)\)
=> \(0+-457000=-457000\)
e, \(\left(16+39\right)+\left(158-16-39\right)\)
=> \(\left(16+39+158-16-39\right)\)
=> \(\left(16-16\right)+\left(39-39\right)+158\)
=> \(0+0+158=158\)