SOLUTION: Find the quadratic equation function that has the given vertex and goes through the given point. Vertex(1,3), point (-2,0) f(x) =

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Find the quadratic equation function that has the given vertex and goes through the given point. Vertex(1,3), point (-2,0) f(x) =      Log On


   



Question 1124651: Find the quadratic equation function that has the given vertex and goes through the given point. Vertex(1,3), point (-2,0) f(x) =
Found 3 solutions by rothauserc, josmiceli, MathTherapy:
Answer by rothauserc(4718) About Me  (Show Source):
You can put this solution on YOUR website!
vertex form of quadratic equation is
:
f(x) = a(x-h)^2 +k, where (h,k) is the vertex
:
we are given the vertex (1,3)
:
f(x) = a(x-1)^2 +3
:
we are given point (-2,0) on the curve
:
a(-2-1)^2 +3 = 0
:
9a +3 = 0
:
9a = -3
:
a = -3/9 = -1/3
:
f(x) = (-1/3)(x-1)^2 +3 =
:
(-1/3)(x^2 -2x +1) +3 =
:
-x^2/3 +2x/3 -1/3 + 3 =
:
-x^2/3 +2x/3 +8/3
:
**************************
f(x) = -x^2/3 +2x/3 +8/3
**************************
:


Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
The form is:
+y+=+a%2Ax%5E2+%2B+b%2Ax+%2B+c+
The x-value of the vertex is at
+x%5Bv%5D+=+-b%2F%282a%29+
Given: x%5Bv%5D+=+1
+-b%2F%282a%29+=+1+
+b+=+-2a+
Now I can say:
+3+=+a%2A1%5E2+%2B+%28-2a%29%2A1+%2B+c+
+c+=+a+%2B+3+
————————
( -2, 0 )
+y+=+a%2Ax%5E2+%2B+%28-2a%29%2Ax+%2B+a+%2B+3+
+0+=+a%2A%28-2%29%5E2+%2B+%28-2a%29%2A%28-2%29+%2B+a+%2B+3+
+0+=+4a+%2B+4a+%2B+a+%2B+3+
+0+=+9a+%2B+3+
+a+=+-1%2F3+
+-2a+=+-2%2A%28-1%2F3%29+
+-2a+=+2%2F3+
+a+%2B+3+=+8%2F3+
—————————————————-
+y+=+%28-1%2F3%29%2Ax%5E2+%2B+%282%2F3%29%2Ax+%2B+8%2F3+
—————————————————-
Check:
(1,3)
+3+=+%28-1%2F3%29%2A1%5E2+%2B+%282%2F3%29%2A1+%2B+8%2F3+
+3+=+9%2F3+
+3+=+3+
————————
( -2, 0 )
+0+=+%28-1%2F3%29%2A%28-2%29%5E2+%2B+%282%2F3%29%2A%28-2%29+%2B+8%2F3+
+0+=+-4%2F3+-4%2F3+%2B+8%2F3+
+0+=+0+
OK

Answer by MathTherapy(10552) About Me  (Show Source):
You can put this solution on YOUR website!

Find the quadratic equation function that has the given vertex and goes through the given point. Vertex(1,3), point (-2,0) f(x) =
Since the vertex of and a point on the parabola are given, we use the vertex form of a parabolic equation, or matrix%281%2C3%2C+f%28x%29%2C+%22=%22%2C+a%28x+-+h%29%5E2+%2B+k%29, with (h, k) being the vertex, and the point (x, y)
matrix%281%2C3%2C+0%2C+%22=%22%2C+a%28-+2+-+1%29%5E2+%2B+3%29 ----- Substituting y for f(x), and then 0 for y, (1, 3) for (h, k), and (- 2, 0) for (x, y) in order to determine "a."
matrix%281%2C3%2C+0%2C+%22=%22%2C+a%28-+3%29%5E2+%2B+3%29
0 = 9a + 3
- 3 = 9a_____matrix%281%2C5%2C+a%2C+%22=%22%2C+-+3%2F9%2C+or%2C+-+1%2F3%29
matrix%281%2C3%2C+f%28x%29%2C+%22=%22%2C+a%28x+-+h%29%5E2+%2B+k%29
------- Substituting -+1%2F3 for "a," and (1, 3) for (h, k)