(15-x)*5+x=15
\(\dfrac{x}{15}=\dfrac{3}{5}-\dfrac{-2}{3}\) ok
\(\Rightarrow\dfrac{x}{15}=\dfrac{9}{15}+\dfrac{10}{15}\)
\(\Rightarrow\dfrac{x}{15}=\dfrac{19}{15}\)
\(\Rightarrow x=19\)
A) x -(25-x)=x-15
B) x-8=-13-8
C) x-(-15)=5-(-19)
D) (x+35)=2x+15+(13-4)
E) 5-2x=15-(-9)-3x
G) x+135=3x-15
a/ x - ( 25 - x) = x - 15
=> x - 25 + x = x - 15
=> 2x - x = -15 + 25
=> x = 10
b/ x - 8 = -13 - 8
=> x = -13 - 8 + 8 = -13
c/ x - (-15) = 5 - (-19)
=> x + 15 = 5 + 19 => x = 5 + 19 - 15 = 9
d/ (x + 35) = 2x + 15 + (13 - 4)
=> x + 35 = 2x + 15 + 13 - 4
=> x - 2x = 15 + 13 - 4 - 35
=> -x = -11 => x = 11
e/ 5 - 2x = 15-(-9) - 3x
=> 5 - 2x = 15 + 9 - 3x
=> -2x + 3x = 15 + 9 - 5
=> x = 19
g/ x + 135 = 3x - 15
=> x - 3x = -15 - 135
=> -2x = -150
=> x = -150/ - 2 = 75
Tính bằng cách thuận tiện
(7/15 x 2/5 + 4/5 x 7/15 - 7/15 x 2/10) : 1/5 = .....…
x-5/2005+x-15/1995<x-2005/5+x-1995/15
3x 4/15 + 2 x 4/15-5 x 4/15
`3xx4/15+2xx4/15-5xx4/15`
`=4/15xx(3+2-5)`
`=4/15xx0`
`=0`
`3 xx 4/15 + 2 xx 4/15 - 5 xx 4/15`
`= 4/15 xx (3 + 2 - 5)`
`= 4/15 xx 0`
`= 0`
\(3\times\dfrac{4}{15}+2\times\dfrac{4}{15}-5\times\dfrac{4}{15}\)
\(=\dfrac{4}{15}\times\left(3+2-5\right)\)
\(=\dfrac{4}{15}\times0\)
\(=0\)
Tìm số tự nhiên x biết: 15/19 x 38/5 < x < 67/15 + 56/15
\(\dfrac{15}{19}\times\dfrac{38}{5}< x< \dfrac{67}{15}+\dfrac{56}{15}\\ \Leftrightarrow6< x< 8,2\\ \Leftrightarrow x\in\left\{7;8\right\}\)
Tính nhanh :
a) 3416 +1025 + 6584 =..................................................................................................................
b) 15 x 2 + 15 x 3 + 15 x 5 =...........................................................................................................
a: =10000+1025=11025
b: =15x(2+3+5)=150
\(a,\left(3416+6584\right)+1025=11025\\ b,15\times\left(2+3+5\right)=150\)
a)
3416 +1025 + 6584 =( 3416+6584)+1025
= 10000+1025
=11025
b) 15 x 2 + 15 x 3 + 15 x 5 = 15.(2+3+5)
= 15. 10
=150
Tính nhanh :
a) 3416 +1025 + 6584 =..................................................................................................................
b) 15 x 2 + 15 x 3 + 15 x 5 =...........................................................................................................
\(a,3416+1025+6584\\ =\left(3416+6584\right)+1025\\ =10000+1025\\ =11025\\ b,15\times2+15\times3+15\times5\\ =15\times\left(2+3+5\right)\\ =15\times10\\ =150\)
a,3416+1025+6584=(3416+6584)+1025=10000+1025=11025b,15×2+15×3+15×5=15×(2+3+5)=15×10=150
a)3416+1025+6584
=(3416+6584)+1025
=10 000+1025
=11 025
Tìm số tự nhiên x biết:
15/19 x 38/5 < x < 67/15 - 56/15
\(\dfrac{15}{19}\times\dfrac{38}{5}< x< \dfrac{67}{15}-\dfrac{56}{16}\\ \dfrac{5\times3\times19\times2}{19\times5}< x< \dfrac{67\times16-56\times15}{15\times16}\\ 3\times2< x< \dfrac{232}{240}\\ 6< x< \dfrac{232}{240}\) (*)
Mà : \(\dfrac{232}{240}< \dfrac{240}{240}=1\\ \)
Nên (*) là vô lí ( Do `6>232/240` )
Vậy \(x\in\varnothing\)
\(\dfrac{15}{17}\) x \(\dfrac{34}{5}\) < x < \(\dfrac{62}{15}\) + \(\dfrac{58}{15}\)
\(\dfrac{20}{29}\) x \(\dfrac{58}{5}\) < x < \(\dfrac{75}{11}\) + \(\dfrac{37}{11}\)
a: =>15/5*34/17<x<120/15
=>6<x<8
=>x=7
b; =>20/5*58/29<x<112/11
=>8<x<112/11
=>x=9 hoặc x=10