Question

Tìm số tự nhiên x,biết:

a)(2600+6400)-3.x=1200

b)[(6.x-72):2-84].28=5628

c)2.x-138=2³.3²

d)42.x=39.42-37.42

Answer 1

a) ( 2600 + 6400 ) - 3 . x = 1200

9000 - 3 . x = 1200

3 . x = 9000 - 1200

3 . x = 7800

x = 7800 : 3

x = 2600

b) [ ( 6 . x - 72 ) : 2 - 84 ] . 28 = 5628

[ ( 6 . x - 72 ) : 2 - 84 ] = 5628 : 28

[ ( 6 . x - 72 ) : 2 - 84 ] = 201

( 6 . x - 72 ) : 2 = 201 + 84

( 6 . x - 72 ) : 2 = 285

( 6 . x - 72 ) = 285 . 2

( 6 . x - 72 ) = 570

6 . x = 570 + 72

6 . x = 642

x = 642 : 6

x = 107

c) 2 . x - 138 = 2³ . 3²

2 . x - 138 = 8 . 9

2 . x - 138 = 72

2 . x = 72 + 138

2 . x = 210

x = 210 : 2

x = 105

d, 42 . x = 39 . 42 - 37 . 42

42 . x = 42 . ( 39 - 37 )

42 . x = 42 . 2

\(\Rightarrow\) x = 2