các bạn ơi giúp mình với : x x 5 + x x 3 = 73.6
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a: =>1/3*4+1/4*5+...+1/x(x+1)=10/39
=>1/3-1/4+...+1/x-1/x+1=10/39
=>1/3-1/(x+1)=10/39
=>1/(x+1)=13/39-10/39=3/39=1/13
=>x+1=13
=>x=12
b: =>15x=150
=>x=10
c: =>120-5x=45
=>5x=75
=>x=15
-12(x-5)+7(3-x)=5
=> -12x+60+21-7x=5
=> -19x+81=5
=>-19x=5-81
=>-19x=-76
=>x=4
Vậy x=4
3/2.(x-5/3)+4/5=x+1
3/2.x-3/2.5/3+4/5=x+1
3/2.x-5/2-x=1+4/5
3/2.x-5/2-x=9/5
3/2.x-x=9/5+5/2
1/2.x=43/10
x=43/10:1/2
x=43/5
`@` `\text {Ans}`
`\downarrow`
\(\left(1-\dfrac{1}{2}\right)\times\left(1-\dfrac{1}{3}\right)\times\left(1-\dfrac{1}{4}\right)\times\left(1-\dfrac{1}{5}\right)...\left(1-\dfrac{1}{1000}\right)\)
`=`\(\left(\dfrac{2}{2}-\dfrac{1}{2}\right)\times\left(\dfrac{3}{3}-\dfrac{1}{3}\right)\times\left(\dfrac{4}{4}-\dfrac{1}{4}\right)...\left(\dfrac{1000}{1000}-\dfrac{1}{1000}\right)\)
`=`\(\dfrac{1}{2}\times\dfrac{2}{3}\times\dfrac{3}{4}\times...\times\dfrac{999}{1000}\)
`=`\(\dfrac{1}{1000}\)
\(=\dfrac{1}{2}.\dfrac{2}{3}.\dfrac{3}{4}.\dfrac{4}{5}.......\dfrac{99}{100}=\dfrac{1}{100}\)
\(x-\left(1-x\right)=5+\left(-1+x\right)\)
\(\Leftrightarrow x-1+x=5-1+x\)
\(\Leftrightarrow2x-1=x+4\)
\(\Leftrightarrow2x-x=1+4\)
\(\Leftrightarrow x=5\)
nè
a: Ta có: 0.25x3=5.60.1250.25x3=5.60.125
⇔x⋅14=134.4⇔x⋅14=134.4
hay x=537,6
b: Ta có: 2.57.5=x:352.57.5=x:35
⇔x:35=13⇔x:35=13
hay x=15x=15
x. 5 + x. 3= 73 ,6
x . ( 5+ 3) = 73, 6
x . 8 = 73, 6
x = 73, 6: 8
x =9 ,2
x x 5 + x x 3 = 73.6
x x (3+5) =73.6
x x 8 =73.6
x =73.6:8
x =9.2
Hok tốt!!!!!!!!!!!!!!!^^