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madmaths · Feb 20, 2011, 05:58 AM

I'm doing cover work for a teacher and I'm having to teach maths! Not my subject and I have no idea about most of the topics! HELP PLEASE! I don't even know where to start!!

Find the gradient of the straight line that passes through the points (3,6) and (-5,-2) and hence find the equation of the line, clearly showing each step of your method.

Thanks: Jane

Unknown008 · Feb 20, 2011, 07:00 AM

You need first the gradient of the line and then the y-intercept, to get the form:

y = mx + c

where m is the gradient and c is the y-intercept.

One quick formula is:

$\frac{y - y_1}{x - x_1} = \frac{y_2 - y_1}{x_2-x_1}$

Where the points $(x_1, y_1)\ and\ (x_2, y_2)$ are the given points.

Substituting in numbers gives you:

$\frac{y - (-2)}{x - (-5)} = \frac{(6) - (-2)}{(3)-(-5)}$