Write the equation of a quadratic function that contains the points (1,21), (2,18), and (-1,9)

The equation of a quadratic function that contains the points (1, 21), (2,18) and (-1, 9) is .

Step-by-step explanation:

A quadratic function is a second order polynomial of the form:

(1)

Where:

- Independent variable.

- Dependent variable.

, , - Coefficients.

From Algebra we understand that a second order polynomial is determined by knowing three distinct points. If we know that , and , then we construct the following system of linear equations:

(2)

(3)

(4)

By algebraic means, the solution of the system is:

, ,

Therefore, the equation of a quadratic function that contains the points (1, 21), (2,18) and (-1, 9) is .

can someone answer this question plz

step-by-step explanation: