In the quadratic problem: A train travels 300km at a uniform speed. If the speed had been 5km an hour more, the journey would have taken 2 hours less. Find the speed of the train?
Here the equation is set as 300/x - 300/x+5 = 2
what I would like to know is why I cant set the equation as 300/x+5 - 300/x = 2?
Is there any way to understand this rule?

can u explain how the equation 300/x-300/x+5 +2 comes?
The question is to solve for x and for this the equation is set as stated above.


The Brainliest Answer!

This Is a Certified Answer

Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
No rule it is simple you see the first time let us assume as t₁ and the second time as t₂ 

now you see t₁ = 300/x and  t₂ = 300/(x+5)

here you see the denominator of t₂ is greater than that of t₁ so from here we can understand logically that t₁ is greater that that of t₂ since they have equal numerator 

Let me make u understand with a simple example let x₁ = 300/y  and x₂ = 300/(y + 5)

Let  y = 10 

so we get x₁ = 30 and x₂ = 20 you see x₁ > x₂ 

so now let us return to the problem ,you see in the same sense we get t₁ > t₂

so we always subtract smaller from greater number to get a positive result 

so thats why we here also do   t₁ - t₂     to get '+'tive 2  
2 5 2
hope i am able to help u ,any problem ask me
Let x be the speed of train in kph
so at speed x kph it takes 300/x hrs to complete journey
At higher speed  x+5 it would take less time and complete journey in 300/(x+5) hrs
   We know 300/(x+5) is less than 300/x by 2 hrs
   That gives 300/x- 300/(x+5)=2