# How do you find the quadratic function given the vertex (2,-4) and the point (1,-1)?

Feb 12, 2016

$y = 3 {\left(x - 2\right)}^{2} - 4$

#### Explanation:

the standard form of a quadratic function in ' vertex form' is :

y $= a {\left(x - h\right)}^{2} + k$
where (h , k ) are the coords of the vertex.

hence : $y = a {\left(x - 2\right)}^{2} - 4$

the other point on the function (1 , -1 ) allows a , to be found.

so -1 = a - 4 → a = 3