Math  /  Algebra

Question6. A quadratic function of the form y=x2+bx+cy=x^{2}+b x+c is shown graphed. (a) What are the xx-intercepts of this parabola? (b) Based on your answer to part (a), write the equation of this quadratic function first in factored form and then in trinomial form.

Studdy Solution

STEP 1

What is this asking? We're looking for the equation of a parabola, given its graph showing *x*-intercepts at 3-3 and 11. Watch out! Don't mix up the signs of the *x*-intercepts when writing the factored form.

STEP 2

1. Find the *x*-intercepts.
2. Write the factored form.
3. Expand to trinomial form.

STEP 3

The graph shows the parabola intersecting the *x*-axis at two points.
Let's find them!

STEP 4

The parabola crosses the *x*-axis at x=3x = -3 and x=1x = 1.
These are our **x-intercepts**, also known as the **roots** or **zeros** of the quadratic function.
So, when y=0y=0, xx can be 3-3 or 11.

STEP 5

Knowing the *x*-intercepts helps us write the factored form of a quadratic equation: y=a(xr1)(xr2)y = a(x - r_1)(x - r_2), where r1r_1 and r2r_2 are the roots, and aa determines how "stretched" or "compressed" the parabola is.

STEP 6

Plugging in our **roots**, we get y=a(x(3))(x1)y = a(x - (-3))(x - 1), which simplifies to y=a(x+3)(x1)y = a(x + 3)(x - 1).

STEP 7

Since the problem states the quadratic is of the form y=x2+bx+cy = x^2 + bx + c, we know that the coefficient of x2x^2 is 11.
This tells us that our **stretching factor**, aa, is also **1**!
So, our factored form is y=(x+3)(x1)y = (x + 3)(x - 1).

STEP 8

To get the trinomial form, we need to **expand** the factored form using the distributive property (also known as FOIL).

STEP 9

Let's multiply! (x+3)(x1)=xx+x(1)+3x+3(1)(x + 3)(x - 1) = x \cdot x + x \cdot (-1) + 3 \cdot x + 3 \cdot (-1).

STEP 10

Simplifying gives us x2x+3x3x^2 - x + 3x - 3.
Combining like terms, we get x2+2x3x^2 + 2x - 3.

STEP 11

(a) The *x*-intercepts are 3-3 and 11. (b) The factored form is y=(x+3)(x1)y = (x + 3)(x - 1), and the trinomial form is y=x2+2x3y = x^2 + 2x - 3.

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