Alain throws a stone off a bridge into a river below. The stone's height (in meters above the water), x seconds after Alain threw it, is modeled by: h(x)=−5x2+10x+15. How many seconds after being thrown will the stone hit the water? seconds
Q. Alain throws a stone off a bridge into a river below. The stone's height (in meters above the water), x seconds after Alain threw it, is modeled by: h(x)=−5x2+10x+15. How many seconds after being thrown will the stone hit the water? seconds
Understand the problem: Understand the problem.We need to find the time when the stone hits the water, which is when its height is 0 meters.
Set up the equation: Set up the equation to find when the height is 0. We need to solve the equation h(x)=−5x2+10x+15=0.
Calculate the discriminant: Calculate the discriminant b2−4ac.Discriminant = b2−4ac=(10)2−4(−5)(15)=100+300=400.
Calculate square root: Calculate the square root of the discriminant. 400=20.
Apply quadratic formula: Apply the quadratic formula to find the values of x.x=2⋅−5−10±20.
Calculate possible values: Calculate the two possible values for x.x1=($−10 + 20) / −10 = 10 / −10 = −1 (This value is not physically meaningful as time cannot be negative).x_2 = (\(-10 - 20) / −10 = x1=($−100 / −10 = x1=($−102 (This is the time in seconds when the stone hits the water).
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