The vertex of a quadratic function

Question

Find the y-intercept and vertex for the following function: f(x)=5x²−7x+c

Express your answers in terms of c where appropriate.

This is very confusing because the variable of c is unknown. Usually on other other quadratic equations the variable of c is given.

Answer 1

The c term is not given so we will simply express our answers in terms of c as the problem asks us to do.

x(v) = -b/(2a) = -7/(2(5)) = -7/10 = -0.7

y(v) = 5(-0.7)^2 + 7(-0.7) + c

y(v) = 5(0.49) - 4.9 + c

y(v) = 2.45 - 4.9 + c

y(v) = - 2.45 + c

So the vertex is (-0.7,-2.45+c)

The y-intercept is (0,c)

Answer 2

vertex = (.7, c- 2.45)

rewrite 5x^2 +7x -c in a(x-h)^2+k vertex from where (h,k)=vertex=(7/10, c-2.45)