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a.3-(-12+3)+x=x-(-12-10)
<=> 3+9+x=x+22
<=>x-x=22-3-9
<=> 0x=10
b,2-x=14-(x+4)
<=>2-x=14-x-4)
<=>x-x=14-4-2
<=>0x=8
c.x-12=14+(6-x)
<=>x-12=14+6-x
<=>x+x=14+6+12
<=>0x=32
a ) x ∈ − 3 4 ; 3 4 b ) x ∈ 2 3 ; − 5 3 ; c ) x ∈ − 3 4 ; 5 4 d ) x ∈ 23 4 ; − 17 4
a
12 * 13 * 14
= 156 * 14
= 2184
b
67 * 12 +33 * 12
= (67 + 33) * 12
= 100 * 12
= 1200
c
100 * 12 + 100 * 88
= (12+88) * 100
= 100 * 100
= 10000
a . 12 x 13 x 14 b) 67 x 12 + 33 x 12 c) 100 x 12 + 100 x 88
= 156 x 14 = ( 67 + 33 ) x 12 = 100 x ( 12 + 88 )
= 2184 = 100 x 12 = 100 x 100
= 1200 = 10000
Ta có :
= 2.[1/10.12+1/12.14+1/14.16+...+1/x.(x+2)] = 19/400 = 2/10.12+2/12.14+2/14.16+...+2/x.(x+2) = 19/400
Mà 2/10.12=1/10-1/12
2/12.14=1/12-1/14
............................................
= 1/10-1/12+1/12-1/14+...+1/x-1/x+2 = 19/400
= 1/10-1/x+2 = 19/400
=>1/x+2 = 1/10-19/400 => 1/x+2=21/400
a ) x = 5 4 x = − 5 4 b ) x = 3 2 x = − 1 2 c ) x = 3 2 x = − 1 2
d ) x = 59 40 x = 61 40 e ) x = 1 3 x = − 1 f ) x = 1 3 x = − 1
1: =7/6:(-21/5)-25*0,2
=-7/6*5/21-5
=-35/126-5
=-5/21-5
=-5/21-105/21=-110/21
3: \(=\dfrac{7}{12}+\dfrac{5}{72}-\dfrac{11}{36}=\dfrac{42+5-22}{72}=\dfrac{25}{72}\)
14 - ( x - 12 ) : 12 = 12
=> ( x - 12 ) : 12 = 14 - 12 = 2
=> x - 12 = 2 x 12 = 24
=> x = 24 + 12
=> x = 36
14-x+12=12.12
14-x+12=144
14-x=144-12
14-x=132
x=14-132
x=-118
vậy x=-118