Tìm x biết : x - 55 = 45
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\(\dfrac{55-x}{1963}\) + \(\dfrac{50-x}{1968}\) + \(\dfrac{45-x}{1973}\) + \(\dfrac{40-x}{1978}\) + 4 = 0
(1 + \(\dfrac{55-x}{1963}\) ) + ( 1 + \(\dfrac{50-x}{1968}\)) + (1+ \(\dfrac{45-x}{1973}\))+ (1 + \(\dfrac{40-x}{1978}\)) = 0
\(\dfrac{1963+55-x}{1963}\) + \(\dfrac{1968+50-x}{1968}\)+\(\dfrac{1973+45-x}{1973}\)+\(\dfrac{1978+40-x}{1978}\)=0
\(\dfrac{2018-x}{1963}\)+\(\dfrac{2018-x}{1968}\)+\(\dfrac{2018-x}{1973}\)+\(\dfrac{2018-x}{1973}\)+\(\dfrac{2018-x}{1978}\)=0
(2018 - \(x\))\(\times\)( \(\dfrac{1}{1963}\)+\(\dfrac{1}{1986}\)+\(\dfrac{1}{1973}\)+) =0
2018 \(-x\) = 0
\(x\) = 2018
\(\dfrac{55-x}{1963}+\dfrac{50-x}{1968}+\dfrac{45-x}{1973}+\dfrac{40-x}{1978}+4=0\)
\(\Rightarrow\text{ }\dfrac{55-x}{1963}+\dfrac{50-x}{1968}+\dfrac{45-x}{1973}+\dfrac{40-x}{1978}+1+1+1+1=0\)
\(\Rightarrow\text{ }\left(\dfrac{55-x}{1963}+1\right)+\left(\dfrac{50-x}{1968}+1\right)+\left(\dfrac{45-x}{1973}+1\right)+\left(\dfrac{40-x}{1978}+1\right)=0\)
\(\Rightarrow\text{ }\dfrac{2018-x}{1963}+\dfrac{2018-x}{1968}+\dfrac{2018-x}{1973}+\dfrac{2018-x}{1978}=0\)
\(\Rightarrow\text{ }\left(2018-x\right)\left(\dfrac{1}{1963}+\dfrac{1}{1968}+\dfrac{1}{1973}+\dfrac{1}{1978}\right)=0\)
Mà \(\dfrac{1}{1963}+\dfrac{1}{1968}+\dfrac{1}{1973}+\dfrac{1}{1978}\ne0\)
\(\Rightarrow\text{ }2018-x=0\)
\(\Rightarrow\text{ }x=2018-0\)
\(\Rightarrow\text{ }x=2018\)
Vậy, \(x=2018.\)
15 x 45 + 15 x 55 = 15 x X 15 x ( 45 + 55 ) = 15 x X 15 x 100 = 15 x X => X = 100 ( đúng thì k cho mị nhá )
câub 55 - 5 x ( x + 3 ) =10
5 x ( x + 3 ) = 55 - 10
5 x ( x + 3 ) = 45
x + 3 = 45 / 5
x + 3 = 9
x = 9 - 3
x = 6
câu a đề sai hoặc thiếu bạn nè
đúng thì kết bn nhé
-[-3x+2(45-x-9x+21-2x)+4x=55
-[-3x+2(24-12x)+4x]=55
-(-3x+48-24x+4x)=55
-(48-23x)=55
23x=55+48
x=103/23
Xem lại dùm mink nha
Đáp án cần chọn là: B
Ta có A=18+36+72+2x màA⋮9;18⋮9;36⋮9;72⋮9⇒2x⋮9⇒x⋮9
Mà 45<x<55⇒x=54
Vậy x=54.
x - 55 = 45
x = 45 + 55
x = 100
x - 55 = 45
x = 55 + 45
x = 100