Equation of a straight line

Is it possible to find the equation of a straight line given two coordinates of that line.

I have a problem I need to solve involves finding the area between a curve and a straight. But I am given only the equation of the curve, I have managed to find two coordinates of the line from differentiating the curve. But I need to know the equation of the line to differentiate it.

Re: Equation of a straight line

Quote:

Originally Posted by

**Googl** **Is it possible to find the equation of a straight line given two coordinates of that line.**

I have a problem I need to solve involves finding the area between a curve and a straight. But I am given only the equation of the curve, I have managed to find two coordinates of the line from differentiating the curve. But I need to know the equation of the line to differentiate it.

**yes** ... find the slope between the two points and determine the equation using either one of the two points, the slope between them, and the point-slope form of a linear equation.

Re: Equation of a straight line

Find the gradient first,

Then using y=mx+c:

Plug in one of the co-ordinates you have into the equation to find c.

Re: Equation of a straight line

Yes, that's what I have found. But when I try different points the c value changes. Here are some points and the straight line:

y = 12x + c

Points (2, 16) (10/3, 0)

Re: Equation of a straight line

Quote:

Originally Posted by

**Googl** Yes, that's what I have found. But when I try different points the c value changes. Mr F says: Surely it is obvious that his statement is absolutely useless unless you show your working,** including how you got 12 as the gradient**.

Here are some points and the straight line:

y = 12x + c

Points (2, 16) (10/3, 0)

..

Re: Equation of a straight line

Hi,

Ignore this. I have found the error. 12 is a negative.

Thanks.

Re: Equation of a straight line

Use $\displaystyle y-y'=m(x-x') $