Question

Which point gives the vertex of f(x) = x2 – 4x + 21? Question 1 options: (–2,–17) (2,17) (–2,17) (2,–17)

Answer 1

Answer:

$(2, 17)$

Step-by-step explanation:

A parabola has the general function: $f(x)=ax^2+bx+c$

In this case we have: $f(x) = x^2 - 4x + 21$

where

$a=1$

$b=-4$

$c=21$

the vertex of a parabola is in the coordinates:

$(\frac{-b}{2a}, \frac{-b^2+4ac}{4a} )$

substituting all of the known values, we get the following:

$(\frac{-(-4)}{2(1)} ,\frac{-(-4)^2+4(1)(21)}{4(1)} )\\\\(\frac{4}{2} ,\frac{-16+84}{4} )\\\\\\(2 ,\frac{68}{4} )\\\\\\(2,17)$

the vertex of  $f(x) = x^2 - 4x + 21$ is at the point (2,17) which is the second option.

Answer 2

Answer:

2,17

Step-by-step explanation: