# Toán Lớp 7: Tìm x A) 1500.(x-7)=3 B) 128-3.(x+4=23 C) [(14.x+26).3+55]:5=35 D) 720:[41-(2x-5)]:2mũ3=2mũ.5

Toán Lớp 7: Tìm x
A) 1500.(x-7)=3
B) 128-3.(x+4=23
C) [(14.x+26).3+55]:5=35
D) 720:[41-(2x-5)]:2mũ3=2mũ.5

TRẢ LỜI

1. truonganhthi
a)
1500.(x-7)=3
=>x-7=3:1500
=>x-7=1/500
=>x=1/500+7
=>x=7,002
b)
128-3(x+4)=23
=>3(x+4)=128-23
=>3(x+4)=105
=>x+4=105:3
=>x+4=35
=>x=35-4
=>x=31
c)
[(14x+26).3+55]:5=35
=>(14x+26).3+55=35×5
=>(14x+26).3+55=175
=>(14x+26).3=175-55
=>(14x+26).3=120
=>14x+26=120:3
=>14x+26=40
=>14x=40-26
=>14x=14
=>x=14:14
=>x=1
d)
720:[41-(2x-5)]:2^3=2^5
=>720:[41-(2x-5)]:8=32
=>90:[41-(2x-5)]=32
=>41-(2x-5)=90:32
=>41-(2x-5)=2,8125
=>2x-5=41-2,8125
=>2x-5=38,1875
=>2x=38,1875+5
=>2x=43,1875
=>x=43,1875:2
=>x=21,59375

Trả lời
2. hoaiphuong85
a) 1500 . ( x – 7) = 3
( x – 7) =  3 : 1500
x – 7 = 0,002
x      = 0,002 + 7
x       = 7,002
b) 128 – 3 ( x +4 ) = 23
3 ( x + 4) = 128 – 23
3 ( x + 4)    = 105
( x + 4)     = 105 : 3
x + 4        =35
x              = 35 – 4
x             = 31
c) [(14. x + 26) . 3 + 55] : 5 = 35
[(14. x + 26) . 3 + 55]     = 35 . 5
(14. x + 26) . 3 + 55      =175
( 14 . x + 26). 3                = 175 – 55
( 14 . x + 26). 3               = 120
( 14 . x + 26)                  = 120 : 3
14 . x + 26                    = 40
14 . x                             = 40- 26
14 . x                            =14
x                              = 14 : 14
x                             = 1
d)720 : [ 41 – ( 2x – 5)] : 2³ = 2^5
720 : [ 41 – ( 2x – 5)] : 8 = 32
720 : 8 :[ 41 – ( 2x – 5)] = 32
90 : [ 41 – ( 2x – 5)]       = 32
[ 41 – ( 2x – 5)]       = 90 : 32
41 – ( 2x – 5)         = 2,8125
( 2x – 5)        = 41 – 2,8125
( 2x – 5)         =38,1875
2x               = 38,1875 + 5
2x             = 43,1875
x            =21,59375

Trả lời