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Given x-intercepts of (-1,0), (6, 0) and point (-2, 2) that lies on the

quadratic graph, which equation below represents the correct quadratic
equation in standard form?

User Eten
by
8.1k points

1 Answer

4 votes

Answer:

y = (-1/3)x^2 - 2x + 5/3

Explanation:

To find the quadratic equation that passes through these points, we can start by using the standard form of a quadratic equation:

y = ax^2 + bx + c

We know that the graph passes through the point (-2,2), so we can substitute these values into the equation:

2 = a(-2)^2 + b(-2) + c

Simplifying this equation, we get:

4a - 2b + c = 2

We also know that the graph has x-intercepts at (-1,0) and (6,0). This means that when x = -1 and x = 6, the value of y (i.e., the height of the graph) is 0. We can use these two points to write two more equations:

0 = a(-1)^2 + b(-1) + c

0 = a(6)^2 + b(6) + c

Simplifying these equations, we get:

a - b + c = 0

36a + 6b + c = 0

Now we have a system of three equations:

4a - 2b + c = 2

a - b + c = 0

36a + 6b + c = 0

We can solve for a, b, and c using any method of solving systems of equations. One way is to use substitution:

From the second equation, we get:

c = b - a

Substituting this into the other two equations, we get:

4a - 2b + (b - a) = 2

36a + 6b + (b - a) = 0

Simplifying these equations, we get:

3a - b = 1

35a + 7b = -b

Multiplying the first equation by 7 and adding it to the second equation, we eliminate b:

21a = -7

a = -1/3

Substituting this value of a into the first equation, we can solve for b:

4(-1/3) - 2b + (b - (-1/3)) = 2

-4/3 - b + b + 1/3 = 2

b = -2

Finally, we can use either of the first two equations to solve for c:

c = a - b = (-1/3) - (-2) = 5/3

So the quadratic equation in standard form is:

y = (-1/3)x^2 - 2x + 5/3

User Rafiek
by
8.3k points

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