a: \(36=3^2\cdot2^2;60=2^2\cdot3\cdot5;90=3^2\cdot2\cdot5\)

=>\(ƯCLN\left(36;60;90\right)=2\cdot3=6\)

=>\(ƯC\left(36;60;90\right)=Ư\left(6\right)=\left\{1;-1;2;-2;3;-3;6;-6\right\}\)

b: \(45=3^2\cdot5;60=2^2\cdot3\cdot5;150=2\cdot3\cdot5^2\)

=>\(ƯCLN\left(45;60;15\right)=3\cdot5=15\)

\(45⋮x;60⋮x;150⋮x\)

=>\(x\inƯC\left(45;60;150\right)\)

=>\(x\inƯ\left(15\right)\)

mà 5<=x<=10

nên \(x=5\)

c: \(45=3^2\cdot5;54=3^3\cdot2;188=2^2\cdot47\)

=>\(ƯCLN\left(45;54;188\right)=1\)

\(45⋮x;54⋮x;188⋮x\)

=>\(x\inƯC\left(45;54;188\right)\)

=>\(x\inƯ\left(1\right)\)

mà 3<x<8

nên \(x\in\varnothing\)

\(a,1999-2000+1=\left(1999+1\right)-2000=2000-2000=0\\ b,450:5+550:5=\left(450+550\right):5=1000:5=200\\ c,188\times7+188\times4-188=188\times\left(7+4-1\right)=188\times10=1880\)

a,1999−2000+1=(1999+1)−2000=2000−2000=0b,450:5+550:5=(450+550):5=1000:5=200c,188×7+188×4−188=188×(7+4−1)=188×10=1880

a) 1999 - 2000 + 1

= ( 1999 + 1 ) - 2000

= 2000 - 2000

= 0

b) 450 : 5 + 550 : 5

= ( 450 + 550 ) : 5 

= 1000 : 5

= 200

c) 188 x 7 + 188 x 4 - 188

= ( 7 + 4 - 1 ) x 188

= 10 x 188

= 1880

\(x-\left(-18\right)=134-\left(34-91\right)\)

⇔\(x+18=134-34+91\)

⇔\(x+18=191\)

⇔\(x=173\)

\(4x+\left(-188\right)=-358+\left(458-124\right)\)

⇔\(4x-188=-358+458-124\)

⇔\(4x-188=-24\)

⇔\(4x=164\)

⇔\(x=41\)

+) x-(-18) = 134 - (34-91)

<=> x +18 = 191

<=> x= 173

+) 4x+(-188) = -358 + (458 - 124)

<=> 4x =164

<=>x =41

41 nha

a) \(-39-\left(15+x\right)=18\)

\(-39-15-x=18\)

\(-54-x=18\)

\(x=-54-18\)

\(x=-72\)

vậy \(x=-72\)

b) \(31-\left(13+x\right)=18.\left(-4\right)\)

\(31-13-x=-72\)

\(18-x=-72\)

\(x=18+72\)

\(x=90\)

vậy \(x=90\)

c) \(58-\left(47+3x\right)=-18-2x\)

\(58-47-3x+2x=-18\)

\(11-x=-18\)

\(x=11+18\)

\(x=29\)

vậy \(x=29\)

d) \(37-\left(115+x\right)=188\)

\(37-115-x=188\)

\(-78-x=188\)

\(x=-78-188\)

\(x=-266\)

vậy \(x=-266\)

a)

\(-39-\left(15+x\right)=18\)

\(\Rightarrow15+x=-39-18\)

\(\Rightarrow15+x=-57\)

\(\Rightarrow x=-57-15\)

\(\Rightarrow x=-72\)

Vậy \(x=-72\)

b)

\(31-\left(13+x\right)=18.\left(-4\right)\)

\(\Rightarrow31-\left(13+x\right)=-72\)

\(\Rightarrow13+x=31-\left(-72\right)\)

\(\Rightarrow13+x=103\)

\(\Rightarrow x=103-13\)

\(\Rightarrow x=90\)

Vậy \(x=90\)

Ta có: \(5^x.5^{x+1}.5^{x+2}\le10^{18}:2^{18}\)

=> \(5^{x+x+1+x+2}\le\left(10:2\right)^{18}\)

=> \(5^{3x+3}\le5^{18}\)

=> 3x+3 < 18

=> 3.(x+1) < 18 

=> x+1 < 18:3

=> x+1 < 6

=> x < 6-1

=> x < 5

Vậy x \(\in\){0; 1; 2; 3; 4; 5}.

150 - 5x . 18 = 118

         5x . 18 = 150-118

         5x . 18 = 32

                5x = 32 : 18

                5x = 16/9

                 x = 16/9 : 5

                 x = 16/45

\(150-5x\times18=118\\ 5x\times18=150-118\\ 5x\times18=32\\ 5x=32:18\\ 5x=\dfrac{16}{9}\\ x=\dfrac{16}{9}:5\\ x=\dfrac{16}{45}\)

Vậy \(x=\dfrac{16}{45}\)

150 - 5x . 18 = 118

         5x . 18 = 150-118

         5x . 18 = 32

                5x = 32 : 18

                5x = 16/9

                 x = 16/9 : 5

                 x = 16/45

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