# Can Anyone Help Me?

I am struck with the questions which include Diophantine equations. I have a lot of them(questions).The question asks :

Find the number of pairs (x,y) of positive integral solutions for the following equation.

$$2x+3y = 763$$

2 years, 9 months ago

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What have you tried? Where did you get stuck?

Check out Linear Diophantine Equations.

Staff - 2 years, 9 months ago

Sir, isn't there a much time saving way ? Because finding the first random solutions takes a lot time even if you go by the Division Algorithm.

- 2 years, 9 months ago

Not particularly.

For small numbers, you can guess. E.g. $$y = 1, x = \frac{760}{2}$$ works. You can also just try $$x = 1, 2, 3, \ldots$$ and hopes it works out (which it eventually will).

The Extended Euclidean Algorithm for an algorithm that guarantees finding the values within a reasonable amount of time. I think it is on the order of $$O ( \log n )$$, instead of testing all values which has the order of $$O(n)$$.

Staff - 2 years, 9 months ago

Hint: $$2x + 3y = 2x + 3y - 6n + 6n = 2(x - 3n) + 3(y + 2n) = 763$$. And find the smallest and largest integer solution of $$x$$ that satisfy the original equation.

- 2 years, 9 months ago