Question

Which equation below has an axis of symmetry of x = 4 over 3?

y = −3x2 − 4x + 5

y = −3x2 + 4x + 5

y = −3x2 − 8x − 1

y = −3x2 + 8x − 1

Question 6 (Multiple Choice Worth 1 points)

[9.03] What is the range of the graph of y = −3x2 − 12x + 5?

All real numbers

y ≤ −2

y ≥ 17

y ≤ 17

Answer 1

For the first one.
You need to check -b/(2a) for each until you find 4/3 as your answer.

Answer 2

For the second one:
Range is all of the possible y values. It takes a bit more analysis than domain.
First find where the vertex will occur (x value) using -b/(2a). I get -2.
Then put that number back into the function as x to find the y... that is where the parabola starts (I get -3(-2)(-2)-12(-2)+5=17).
Then see if it is right side up or upside down. This one is opening downward because of the minus sign in front... so for y-values (range), it starts at 17 and goes down.