Answer:
The second degree polynomial is f(x) = 4x² - 28x + 40
Explanation:
* Lets revise the general form of the second-degree polynomial
- The general form of the second degree polynomial is
f(x) = ax² + bx + c, where a , b , c are constant
- The highest power of the variable that occurs in the polynomial
is called the degree of a polynomial.
- The leading term is the term with the highest power, and its
coefficient is called the leading coefficient.
- The leading coefficient is the coefficient of x²
∴ a = 4
∴ f(x) = 4x² + bx + c
- The roots of a polynomial are also called its zeroes, because
the roots are the x values at which the function equals zero
∴ When f(x) = 0, the values of x are 5 and 2
* To find the value of b and c substitute the values of x in f(x) = 0
- At x = 5
∵ 4(5)² + b(5) + c = 0 ⇒ simplify it
∴ 100 + 5b + c = 0 ⇒ subtract 100 from both sides
∴ 5b + c = -100 ⇒ (1)
- At x = 2
∵ 4(2)² + b(2) + c = 0 ⇒ simplify it
∴ 16 + 2b + c = 0 ⇒ subtract 16 from both sides
∴ 2b + c = -16 ⇒ (2)
- Subtract (2) from (1)
∴ 3b = -84 ⇒ divide both sides by 3
∴ b = -28
- Substitute the value of b in (1) or (2) to find c
∵ 2(-28) + c = -16
∴ -56 + c = -16 ⇒ add 56 to both sides
∴ c = 40
∴ f(x) = 4x² - 28x + 40
* The second degree polynomial is f(x) = 4x² - 28x + 40