Question

How do you find the vertex and intercepts for `f(x)=5x^2+9x+7`?

Answer 1

Find vertex and intercepts for `f(x) = 5x^2 + 9x + 7`

Explanation:

x-coordinate of vertex:
`x = (-b)/(2a) = -9/10.`
y-coordinate of vertex:
`y = f(-9/10) = 5(81/100) - 9(9/10) + 7 = 405/100 - 81/10 + 7 =`
`= 295/100 = 59/20`
To find y-intercept, make x = 0 --> f(x) = 7
To find x-intercepts make y = 0 and solve `5x^2 + 9x + 7 = 0`
`D = b^2 - 4ac = 81 - 140 < 0`. Since D < 0, there are no x-intercepts.

Answer 2

Have a look at http://socratic.org/s/aq6riwAj
`color(red)("It will show you a trick worth remembering!")`