Question

PLEASE HELP
Your friend, Patricia, is having a hard time understanding the concept behind the domain and range of a parabola. Using complete sentences, explain the meaning of the domain and range of the graph of
y = −x2 + 4x − 21 and how to find both. Keep in mind, your goal is to help Patricia understand the "concepts", not just how to use the steps.

Answer 1

@ Solmyr
do you know if the parabola is opening upward or downward?

Answer 2

no

Answer 3

if y = - x2 then its downward
if y= + x2... then its upward

note theres also parabola that opens sideways on the left or at the right

Answer 4

therefore this type of parabola y = −x2 + 4x − 21 is opens upward or downward ?

Answer 5

it is essential to know if the parabola is opening upward or downward or sideways.. :D

Answer 6

Assuming your parabola is y = ax^2 + bx + c: The domain is always all real numbers...

To find range, find the vertex. If it opens upward, the range will be [y-coord. of vertex, infinity) Positive 'a' opens up

If it opens downward, the range will be (-infinity, y-coord. of vertex] Negative 'a' opens downward