xin hãy giúp tôi tôi k bt làm

Đáp án:

$\text{ S = {100}}$

Giải thích các bước giải:

$\dfrac{x-45}{55}+\dfrac{x-47}{53}=\dfrac{x-55}{45}+\dfrac{x-53}{47}$

$⇔\left(\dfrac{x-45}{55}+1\right)+\left(\dfrac{x-47}{53}+1\right)=\left(\dfrac{x-55}{45}+1\right)+\left(\dfrac{x-53}{47}+1\right)$

$⇔\dfrac{x-100}{55}+\dfrac{x-100}{53}-\dfrac{x-100}{45}-\dfrac{x-100}{47}=0$

$⇔\left(x-100\right)\left(\dfrac{1}{55}+\dfrac{1}{53}-\dfrac{1}{45}-\dfrac{1}{47}\right)=0$

$⇔x-100=0$ $\left(vì\:\dfrac{1}{55}+\dfrac{1}{53}-\dfrac{1}{45}-\dfrac{1}{47}\ne 0\right)$

$⇔x=100$

$\text{Vậy S = {100}}$