Thread: intersection of lines

How would you determine if lines intersected or not

if the lines were something like

y=-x-2

and

y=x^2+2-4

Well since you have two expressions involving x's and y's you can put them together.

and so by equating the y's.

So you need to solve to get the x co-ordinate. The y co-ordinate can then be found by substituting this x value into one of the two equations (they should give the same answer if you've done it right!).

Originally Posted by Showcase_22

Well since you have two expressions involving x's and y's you can put them together.

and so by equating the y's.

So you need to solve to get the x co-ordinate. The y co-ordinate can then be found by substituting this x value into one of the two equations (they should give the same answer if you've done it right!).

would i just collect like terms and factor or how would i solve that?

Exactly!



Here's the first step: .

Originally Posted by william

How would you determine if lines intersected or not

if the lines were something like

y=-x-2

and

y=x^2+2-4

As far as I know y = x^2 + 2x - 4 is not a line... Its a parabola

Originally Posted by Isomorphism

As far as I know y = x^2 + 2x - 4 is not a line... Its a parabola

AH YES! thank you i could simply graph both and see where they intersect,if anywhere

Simultaneous equations are faster than just graphing them.

What if you have two lines that intersect at (100,1000000)? It would be very hard to draw a graph for that!