Section 2.2 Quadratic Functions Chapter 2 Polynomial and Rational Functions
277
277
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277
− 6
44. f ( x) = 6 x
2
− 6 x
a. a = 6. The parabola opens upward and has
minimum value.
52. (h, k ) = (−8, −6)
f ( x ) = 2 ( x − h )
2
+ k
= 2[x − (−8)]
2
+ (−6)
= 2 ( x + 8)
2
− 6
b. x =
−b
=
6
=
1
2a 12 2 53. Since the vertex is a maximum, the parabola opens
1 1
2
f
= 6
1
down and a = −3 .
(h, k ) = (−2, 4)
2 2 2
=
6
− 3 =
3
−
6
=
−3
4 2 2 2
f ( x ) = −3( x − h )
2
+ k
= −3[x − (−2)]
2
+ 4
The minimum is
−3
2
at x =
1
.
2
= −3( x + 2)
2
+ 4
54. Since the vertex is a maximum, the parabola opens
c. domain: (−∞, ∞)
range:
−3
, ∞
down and a = −3 .
2
45. Since the parabola opens up, the vertex (−1, −2) is a
minimum point.
domain: (−∞, ∞) . range: [−2, ∞)
46. Since the parabola opens down, the vertex (−3, −4)
is a maximum point.
domain: (−∞, ∞) . range: (−∞, −4]
47. Since the parabola has a maximum, it opens down
from the vertex (10, −6) .
domain: (−∞, ∞) . range: (−∞, −6]
48. Since the parabola has a minimum, it opens up from
the vertex (−6,18) .
domain: (−∞, ∞) . range: [18, ∞)
49. (h, k ) = (5, 3)
(h, k ) = (5, −7 )
f ( x ) = −3 ( x − h )
2
+ k
= −3 ( x − 5)
2
+ (−7 )
= −3 ( x − 5)
2
− 7
55. Since the vertex is a minimum, the parabola opens
up and a = 3 .
(h, k ) = (11, 0)
f ( x ) = 3( x − h )
2
+ k
= 3( x −11)
2
+ 0
= 3( x −11)
2
56. Since the vertex is a minimum, the parabola opens
up and a = 3 .
(h, k ) = (9, 0)
f ( x ) = 3( x − h )
2
+ k
= 3( x − 9)
2
+ 0
= 3( x − 9)
2
f ( x ) = 2 ( x − h )
2
+ k = 2 ( x − 5)
2
+ 3
57. a. y = −0.01x
2
+ 0.7 x + 6.1
a = −0.01, b = 0.7, c = 6.1
50. (h, k ) = (7, 4)
f ( x ) = 2 ( x − h )
2
+ k = 2 ( x − 7 )
2
+ 4
x-coordinate of vertex
=
−b
=
−0.7
= 35
2a 2 (−0.01)
51. (h, k ) = (−10, −5) y-coordinate of vertex
2
f ( x ) = 2 ( x − h )
2
+ k y = −0.01x + 0.7 x + 6.1
2
= 2[x − (−10)]
2
+ (−5)
y = −0.01(35) + 0.7(35) + 6.1 = 18.35
= 2 ( x +10)
2
− 5
The maximum height of the shot is about 18.35
feet. This occurs 35 feet from its point of release.