In the xy-coordinate plane, the graph of the equation y = 3x² - 12x - 36 has zeros at x = a and x = b, where a < b. The graph has a minimum at (c,-48). What are the values of a, b, and c?

A.) a = 2, b = 4, c = 2

B.) a = -2, b = 6, c = 2

C.) a = -3, b = 3, c = 0

D.) a = 3, b = 6, c = 2

A.) a = 2, b = 4, c = 2

B.) a = -2, b = 6, c = 2

C.) a = -3, b = 3, c = 0

D.) a = 3, b = 6, c = 2

First, find the zeros of the equation. When finding zeros of a quadratic equation, you are finding the x-intercepts. At the x-intercept, the value of y is 0. To find the x-intercepts, substitute 0 for y.

3x² - 12x - 36 = 0 {substituted 0 for y}

3(x² - 4x - 12) = 0 {factored out the greatest common factor, 3}

3(x - 6)(x + 2) = 0 {factored into two binomials}

x - 6 = 0 or x + 2 = 0 {set each factor equal to 0}

x = 6 or x = -2 {solved each equation for x}

It is given that the zeros are at x = a and x = b, and since it is also given that a < b, then

It is given the graph has a minimum at (c,-48). A minimum of a quadratic equation is, graphically, the vertex of the parabola. Since the minimum is at (c,-48), then the y-coordinate of the vertex is -48. To find out what x is when y is -48, substitute -48 in for y into the equation and you will be finding the value of c.

-48 = 3x² - 12x - 36 {substituted -48 in for y}

3x² - 12x + 12 = 0 {added 48 to each side}

3(x² - 4x + 4) = 0 {factored out the greatest common factor, 3}

3(x - 2)(x - 2) = 0 {factored into two binomials}

x - 2 = 0 {set each factor equal to 0}

x = 2 {added 2 to each side}

The value of x, when y is -48, is 2. Therefore, the x-coordinate of the vertex is 2, meaning

**y = 3x² - 12x - 36**3x² - 12x - 36 = 0 {substituted 0 for y}

3(x² - 4x - 12) = 0 {factored out the greatest common factor, 3}

3(x - 6)(x + 2) = 0 {factored into two binomials}

x - 6 = 0 or x + 2 = 0 {set each factor equal to 0}

x = 6 or x = -2 {solved each equation for x}

It is given that the zeros are at x = a and x = b, and since it is also given that a < b, then

**a = -2**and**b = 6**.It is given the graph has a minimum at (c,-48). A minimum of a quadratic equation is, graphically, the vertex of the parabola. Since the minimum is at (c,-48), then the y-coordinate of the vertex is -48. To find out what x is when y is -48, substitute -48 in for y into the equation and you will be finding the value of c.

**y = 3x² - 12x - 36**-48 = 3x² - 12x - 36 {substituted -48 in for y}

3x² - 12x + 12 = 0 {added 48 to each side}

3(x² - 4x + 4) = 0 {factored out the greatest common factor, 3}

3(x - 2)(x - 2) = 0 {factored into two binomials}

x - 2 = 0 {set each factor equal to 0}

x = 2 {added 2 to each side}

The value of x, when y is -48, is 2. Therefore, the x-coordinate of the vertex is 2, meaning

**c = 2**.**B.) a = -2, b = 6, c = 2***Ask Algebra House*