a: \(35=5\cdot7;130=5\cdot2\cdot13\)

=>\(BCNN\left(35;130\right)=5\cdot7\cdot2\cdot13=910\)

\(a⋮35;a⋮130\)

=>\(a\in BC\left(35;130\right)\)

mà a nhỏ nhất

nên a=BCNN(35;130)=910

b:

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

=>\(BCNN\left(45;60\right)=3^2\cdot5\cdot2^2=180\)

 \(a⋮45;a⋮60\)

=>\(a\in BC\left(45;60\right)\)

=>\(a\in B\left(180\right)\)

mà a<500

nên \(a\in\left\{180;360\right\}\)

x : 15;180=> x E BC khác 0

15=3.5

180=2^2.3^2.5

BCNN(15,180):3^2.2^2.5=180

4.120+[45:9+15-(x+1)]=500

480+[45:9+15-(x+1)]=500

45:9+15-(x+1)=500-480

45:9+15-(x+1)=20

5+15-(x+1)=20

20-(x+1)=20

x+1=20-20

x+1=0

x=0-1

x=-1

=>4.120+[45:9+15-(x+1)]=500

=>480+[45:9+15-(x+1)]=500

=>45:9+15-(x+1)=500-480

=>45:9+15-(x+1)=20

=>5+15-(x+1)=20

=>20-(x+1)=20

=>x+1=20-20

=>x+1=0

=>x=0-1

=> x=-1

X là: 500÷25×100=2000

Số x là:
\(500:25\times100=2000\)
Đáp số: 2000

4 . 120 + [45 : 9 +15 . (x + 1) = 500

480 + [45 : 9 +15 . (x + 1) = 500

45 : 9 +15 . (x + 1) = 500-480

45 : 9 +15 . (x + 1) = 20

5 +15 . (x + 1) = 20

15 . (x + 1) = 20-5

15 . (x + 1) = 15

x + 1=15:15

x + 1=1

x=1-1

x=0

= 0

tick cho mink nha

4.120+[45:9+15(x+1)]=500

=>480+[5+15(x+1)]=500

=>5+15(x+1)=20

=>15(x+1)=15

=>x+1=1

=>x=0

4.120+[45:9+15(x+1)]=500

480+[5+15x+15]=500

480+5+15x+15=500

500+15x=500

15x=0

x=0