Question

The minimum of the graph of a quadratic function is located at (–1, 2). The point (2, 20) is also on the parabola. Which function represents the situation?

A.f(x) = (x + 1)2 + 2
B.f(x) = (x – 1)2 + 2
C.f(x) = 2(x + 1)2 + 2
D.f(x) = 2(x – 1)2 + 2

Answer 1

Minimum wykresu funkcji kwadratowej znajduje się w ( -1, 2). Punkt ( 2 , 20) jest również od paraboli. Która funkcja reprezentuje sytuację?
Canonical form of the function
f(x) = a* (x - p)² + q

A .f(x) = (x + 1)² + 2 ⇔ p= -1 , q = 2
B. f(x) = (x – 1)² + 2 we reject
C. f(x) = 2(x + 1)² + 2 ⇔ p = -1 , q = 2
D .f(x) = 2(x – 1)² + 2 we reject

The point (2,20) substitute
A f(x) = (x +1)² + 2
20 = (2 + 1 )² + 2
20 ≠ 9 +2
20 ≠ 11 we reject

D f(x) = 2* (x + 1)² + 2
20 = 2* (2+1)² + 2
20 = 2 * 3² + 2
20 = 2 * 9 + 2
20 = 18 + 2

Reply C