## Solmyr 2 years ago 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.

1. mark_o.

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

2. Solmyr

no

3. mark_o.

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

4. mark_o.

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

5. mark_o.

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

6. mark_o.

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

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