Answer:
b = 4
Step-by-step explanation:
the equation of a parabola in vertex form is
y = a(x - h)² + k
where (h, k ) are the coordinates of the vertex and a is a multiplier
here ( h, k ) = (2, 5 ) , then
y = a(x - 2)² + 5
to find a substitute any point on the parabola into the equation
using (0, 1 ) then
1 = a(0 - 2)² + 5 ( subtract 5 from both sides )
- 4= a(- 2)²= 4a ( divide both sides by 4 )
- 1 = a
then
y = - ( x - 2)² + 5
= - (x² - 4x + 4) + 5
= - x² + 4x - 4 + 5
= - x² + 4x + 1 ← in the form ax² + bx + c
with b = 4
