intercepts and cost

[marshall1432]

1. Find the y-intercept(s) of the parabola given by the function f(x) = 3x2 + 4.

my answer: insert f(x) in for the y function and graph, find points.

2. Find the x-intercept(s), if any, of the parabola given by the function f(x) = 2x2 + 4x - 6.

my answer: same as #1, just find the x values

3. Find the axis of symmetry of the parabola given by the function f(x) = -x2 + 2x + 1.

my answer: i don't know, can someone shoe me step by step on this one.

4. Find the vertex of the parabola given by the function f(x) = 4x2 - 2x, expressing non-integer values in fractional form. State whether the parabola opens up or down.

my answer: I believe it opens down, but I can't get it to graph exactly right.

5. The daily cost C (in dollars) to produce x portable 12-inch TVs is given by
C(x) = x2 - 60x + 3000
How many TVs should be produced to minimize the cost? What is the minimum cost?

my answer: i substituted 400 in and the number was really high, and the same for 4000, just to see if i was getting close to the answer. i was wondering if there might be a possible formula to use on this one? thanks.

 

[skeeter]

1. Find the y-intercept(s) of the parabola given by the function f(x) = 3x2 + 4.

if you mean f(x) = 3x^2 + 4, y-intercept is f(0)

my answer: insert f(x) in for the y function and graph, find points.

2. Find the x-intercept(s), if any, of the parabola given by the function f(x) = 2x2 + 4x - 6.

x-intercepts are where f(x) = 0 ... 2x^2 + 4x - 6 = 0
x^2 + 2x - 3 = 0
(x + 3)(x - 1) = 0
you finish

my answer: same as #1, just find the x values

3. Find the axis of symmetry of the parabola given by the function f(x) = -x2 + 2x + 1.

for a parabola y = ax^2 + bx + c, the axis of symmetry is the line x = -b/(2a)

my answer: i don't know, can someone shoe me step by step on this one.

4. Find the vertex of the parabola given by the function f(x) = 4x2 - 2x, expressing non-integer values in fractional form. State whether the parabola opens up or down.

no, it opens up ... vertex is at x = -b/(2a)

my answer: I believe it opens down, but I can't get it to graph exactly right.

5. The daily cost C (in dollars) to produce x portable 12-inch TVs is given by
C(x) = x2 - 60x + 3000
How many TVs should be produced to minimize the cost? What is the minimum cost?

minimum will occur at the vertex ... I've shown you how to find the x-value of the vertex in two previous problems

my answer: i substituted 400 in and the number was really high, and the same for 4000, just to see if i was getting close to the answer. i was wondering if there might be a possible formula to use on this one? thanks.

 

[marshall1432]

ok, on number 2 is it x=-3, x=1?