Problem 1633. Find the right x in a 1. order Polynomal (y = m*x+c)

Created by Martin

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Given two points in a Cartesian coordinate system, find the x-value on the line y = m*x+b where the y-value is equal to a given value c.
e.g.: we have the points P1(1,2) and P2(3,6) and we want wo know at which x-value y is equal to c = 8; The input is: x = [1 3], y = [2,6], c = 8.
The answer is 4.
Consider the possibility that there isn't any solution (return NaN) of that there is an infinity amount of points (return Inf). Additionally consider that the point could represent a vertial line.
Good Luck!

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Last Solution submitted on Dec 29, 2025

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Dan on 10 Jun 2013

I don't understand the meaning of the problem. If y=c then x=0. Enlighten me, please.

Carlos Adrian Vargas Aguilera on 30 Jun 2013

If y=mx+b, when y=c, x=?

Martin on 23 Jul 2013

Hi everyone:
Dan: in my mathematical understanding (correct me if I am wrong): if y=c the slope m of the curve is 0. but for all x the condition y = c is correct, so x should be infinite
Or is there some error in the solution?

Rafael S.T. Vieira on 4 Oct 2020

The problem description needs to be improved, maybe to something like: Given two points in a Cartesian coordinate system, find the x-value on the line y = a*x+b in which the y-value is equal to a given value c.

goc3 on 8 Oct 2020

The description has been updated.

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