1. ## solving a equation

hi would I solve equations such as

y=-3x+2

and

y=2x^2-7x-4

by factorising or using the quad formula, as I need to find where the above intersect on a graph.

Many thanks

Dave

2. ## Re: solving a equation

Originally Posted by davellew69
hi would I solve equations such as

y=-3x+2

and

y=2x^2-7x-4

by factorising or using the quad formula, as I need to find where the above intersect on a graph.

Many thanks

Dave
At intersection 2x^2-7x-4= -3x+2 So 2x^2 -4x -6=0 Divide both sides by 2 giving x^2-2x-3=0 Now factorize and get two values for x.
Sub these back into y= -3x+2 to get the corresponding values of y.

3. ## Re: solving a equation

This is just a simple simultaneous equation. There will of course be 2 intersection points. $y=2x^2-7x-4$ is a parabola and $y=-3x+2$ will intersect it at 2 points.

as $y=y$ then $2x^2-7x-4=-3x+2$

Therefore, $2x^2-7x-4=-3x+2=2x^2-4x-6$

$\frac{2x^2-4x-6}{2} = x^2-2x-3$

This is a quadratic, so factorise this equation and it will give you two points for $x$. Put these back into the equation, and you will retrive the values for $y$.