how can i find the equation for a function that includes the points:

(0,4) and
(2,0)

i was attempting to use substitution or simultaneous equations but it doesn't work cause I can't substitute the y intercept.

it ends up being 4=c

so i dont konw what to do

2. Hello juliak
Originally Posted by juliak
how can i find the equation for a function that includes the points:

(0,4) and
(2,0)

i was attempting to use substitution or simultaneous equations but it doesn't work cause I can't substitute the y intercept.

it ends up being 4=c

so i dont konw what to do
I'm not sure what type of equation you're looking for, since you've headed this post "Quadratics". But the simplest equation through two points will be a straight line, which will be of the form $\displaystyle y = mx + c$.

So, if we start there, and put in the two pairs of values:

When $\displaystyle x = 0, y = 4$. So $\displaystyle 4 = 0m + c \Rightarrow c = 4$

When $\displaystyle x=2, y=0$. So $\displaystyle 0 = 2m+4 \Rightarrow m = -2$

So one possible equation is $\displaystyle y = -2x + 4$.

If you're looking for a quadratic equation - one of the form $\displaystyle y = ax^2 +bx + c$ - there will be an infinite number passing through just two points, so you'll need more information if you're going to get a single answer.

Hope that helps.