Question

If the points (-1,4) and (2,13) are on the graph of the quadratic function f(x) = 7x^2 + bx + c , what are the values of b and c ?

Answer 1

we can just put the values of the given points,in the equation `f(x) = 7x^2 +bx +c`

So,for `x=-1,f(x) =4`

So, `4 =7-b+c`

or, `b-c=3`...1

And, for `x=2,f(x)=13`

so, `13=28 +2b+c`

or, `2b+c = -15`....2

Solving 1 and 2 we get,

`b=-4` and, `c=-7`