Algebra 2 Help?

1. What is the y-intercept of the graph of y = -x² - 2x + 5?

B. 5

2. What is the axis of symmetry of the graph of y = 3x² - 9x + 12

B. x = 3/2

3. What are the coordinates of the vertex of y = x² - 4x - 5?

A. (2, -9)


4. What is the vertex for the equation f(x) = -5(x + 4)² - 10?

D. {-4. -10}

1.
When x = 0 :
y = -(0)² - 2(0) + 5
y = 5
Hence, y-intercept = 5

The answer: B. 5


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2.
y = 3x² - 9x + 12
y = 3[x² - 3x] + 12
y = 3[x² - 3x + (3/2)²] - 3*(3/2)² + 12
y = 3[x - (3/2)]² + (21/4)

Hence, the axis of symmetry of the graph is x - (3/2) = 0, i.e.
x = 3/2

The answer: x = 3/2


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3.
(h, k) is the vertex of y = a(x - h) + k

y = x² - 4x - 5
y = (x² - 4x) - 5
y = (x² - 4x + 2²) - 2² - 5
y = (x - 2)² + (-9)
Hence, the vertex is (2, -9)

The answer: A. (2, -9)


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4.
(h, k) is the vertex of f(x)= a(x - h) + k

f(x) = -5(x + 4)² - 10
f(x) = -5[x - (-4)]² + (-10)
Hence, the vertex is (-4, -10)

The answer: D. (-4, -10)