7. Evaluate the discriminant for each equation, then use it to predict the number and kind of solutions for each equation. (a) a? - 8x + 16 = 0 (b) 3a2 + 5x + 2 = 0 (c) 9a2 + 11a +4 = 0

Elementary Algebra
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ISBN:9780998625713
Author:Lynn Marecek, MaryAnne Anthony-Smith
Publisher:Lynn Marecek, MaryAnne Anthony-Smith
Chapter10: Quadratic Equations
Section10.4: Solve Applications Modeled By Quadratic Equations
Problem 160E: A city planner wants to build a bridge across a lake in a park. To find the length of the bridge, he...
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7. Evaluate the discriminant for each equation, then use it to predict the number and kind of solutions
for each equation.
(a) a? - 8x + 16 = 0
(b) 3x? + 5a + 2 0
(c) 9a2 + 11z +4 0
8. A landscape architect has included a rectangular flower bed measuring 9 ft. by 5 ft. in her plans for
a new building. She wants to use two colors of flowers in the bed, one in the center and the other for
a border of the same width on all four sides. If she has enough plants to cover 24 ft? for the border,
how wide can the border be?
9. A rectangular piece of metal is 10 in. longer than it is wide. Squares with sides 2 in. long are cut from
the four corners and the flaps are folded upward to form an open box. If the volume of the box is 832
in?, what were the original dimensions of the piece of metal?
10. A kite is flying on 50 ft. of string. It's vertical distance from the ground is 10 ft. more than it's
horizontal distance from the person flying it. Assuming that the string is being held at ground level,
find it's horizontal distance from the person and it's vertical distance from the ground.
11. A building is 2 ft. from a 9-ft. fence that surrounds the property. A worker wants to wash a window
in the building 13 ft. from the ground. He plans to place the ladder over the fence so it rests against
the building. He decides he should place the ladder 8 ft. from the fence for stability. To the nearest
tenth of a foot, how long a ladder will he need?
12. An astronaut on the moon throws a baseball upward. The astronaut is 6 ft., 6 in. tall and the initial
velocity of the ball is 30 ft. per second. The height s of the ball in feet is given by the equation
s= -2.71 + 30t +6.5,
where t is the number of seconds after the ball was thrown.
(a) After how many seconds is the ball 12 ft. above the moon's surface? Round to the nearest
hundredth.
(b) How many seconds will it take for the ball to return to the surface? Round to the nearest
hundredth.
(c) After how many seconds is the ball 100 ft. above the moon's surface? Round to the nearest
hundredth.
Transcribed Image Text:7. Evaluate the discriminant for each equation, then use it to predict the number and kind of solutions for each equation. (a) a? - 8x + 16 = 0 (b) 3x? + 5a + 2 0 (c) 9a2 + 11z +4 0 8. A landscape architect has included a rectangular flower bed measuring 9 ft. by 5 ft. in her plans for a new building. She wants to use two colors of flowers in the bed, one in the center and the other for a border of the same width on all four sides. If she has enough plants to cover 24 ft? for the border, how wide can the border be? 9. A rectangular piece of metal is 10 in. longer than it is wide. Squares with sides 2 in. long are cut from the four corners and the flaps are folded upward to form an open box. If the volume of the box is 832 in?, what were the original dimensions of the piece of metal? 10. A kite is flying on 50 ft. of string. It's vertical distance from the ground is 10 ft. more than it's horizontal distance from the person flying it. Assuming that the string is being held at ground level, find it's horizontal distance from the person and it's vertical distance from the ground. 11. A building is 2 ft. from a 9-ft. fence that surrounds the property. A worker wants to wash a window in the building 13 ft. from the ground. He plans to place the ladder over the fence so it rests against the building. He decides he should place the ladder 8 ft. from the fence for stability. To the nearest tenth of a foot, how long a ladder will he need? 12. An astronaut on the moon throws a baseball upward. The astronaut is 6 ft., 6 in. tall and the initial velocity of the ball is 30 ft. per second. The height s of the ball in feet is given by the equation s= -2.71 + 30t +6.5, where t is the number of seconds after the ball was thrown. (a) After how many seconds is the ball 12 ft. above the moon's surface? Round to the nearest hundredth. (b) How many seconds will it take for the ball to return to the surface? Round to the nearest hundredth. (c) After how many seconds is the ball 100 ft. above the moon's surface? Round to the nearest hundredth.
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