Question

Write the standard form of the quadratic equation modeled by the points shown in the table below.

Answer 1

y = 2x² - 5x + 7

Explanation:

General form of a quadratic is:

y = Ax² + Bx + C

Using the given points, construct equations and solve for A,B and C.

When x = 0, y = 7

7 = A(0)² + B(0) + C

C = 7

y = Ax² + Bx + 7

When x = -1, y = 14

14 = A(-1)² + B(-1) + 7

A - B = 7

A = 7 + B

When x = 1, y = 4

4 = A(1)² + B(1) + 7

A + B = -3

(7 + B) + B = -3

2B = -10

B = -5

A = 7 + (-5)

A = 2

y = 2x² - 5x + 7

Answer 2

General form of a quadratic is:

y = Ax² + Bx + C

• Using the given points, construct equations and solve for A,B and C.

1. When x = 0, y = 7

7 = A(0)² + B(0) + C

C = 7

y = Ax² + Bx + 7

When x = -1, y = 14

14 = A(-1)² + B(-1) + 7

A - B = 7

A = 7 + B

When x = 1, y = 4

4 = A(1)² + B(1) + 7

A + B = -3

(7 + B) + B = -3

2B = -10

B = -5

A = 7 + (-5)

A = 2

y = 2x² - 5x + 7