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**naturewild****Member**- Registered: 2005-12-04
- Posts: 30

Prove : The perpendicular distance from a point P(x1,y1) to the straight line whose equation is Ax + By + c = 0 is

d = absolute value (Ax1 + By1 + c) / square root (A² + B²)

Also another problem not related to geometry is this :

When an integer is divided by 15, the remainder is 7. Find the remainders when the same integer is divided by 3 and 5.

Thanks in advance!

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**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 21,319

naturewild, I shall attempt the second problem first.**When an integer is divided by 15, the remainder is 7. **

Therefore, the number is of the form 15n+7, where n is a certain Natural number. When 15n+7 is divided by 5, since 15n is divisible by 5, the remainder is what it would be when 7 is divided by 5, hence, the remainder is 2.When 15n+7 is divided by 3, since 15n is divisible by 3, the remainder is what it would be when 7 is divided by 3, hence the remainder is 1.

It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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**naturewild****Member**- Registered: 2005-12-04
- Posts: 30

Thanks for the solution to the second problem. Your coloring makes it so easy to understand.

Thanks once again ^^

Actually I have one more problem I'm stuck with, but I'm satisfied with only these 2 solutions ^_^

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