# Straight lines

How do you find the line's equation if two points are given?

Find the gradient (rise/run). We know m, we know the x and y coordinates of the point. Using one point, plug these into y=mx+c and rearrange to find c.

Is the run horizontal or vertical?

Horizontal

How do you know if two lines are parallel?

If m1=m2. M is the gradient

How do you find the x-intercept?

In y=mx+c, use y=0, then solve for x.

How do you check if a point lies on a line?

Plug the x and y coordinates of the point into y=mx+c, and check if you get a contradiction (e.g. 7=6), or a true statement (e.g. 6=6).

How do you solve the simultaneous equations of 2 lines?

See where they cross on a graph and the x and y coordinates of this point are the answer

What is m in y=mx+c?

The gradient

What is c in y=mx+c?

The y-intercept (where the straight line crosses the y-axis)

How can you check if two lines meet?

Use a method for simultaneous equations, if they are solvable, the two lines meet.

Is the rise horizontal or vertical?

Vertical

How do you find the line's equation if the gradient and one point are given?

We know m, we know the x and y coordinates of the point. Plug these into y=mx+c and rearrange to find c.

What is the formula for finding the gradient of a line?

m=rise/run

What is the equation for every straight line?

y=mx+c