Question

The path traveled by a bottlenose dolphin as it jumps out of water is modeled by the equation y = −0.4x2 + 3x, where y is the height above water and x is the horizontal distance in feet. If a beam of light is shone upward at an angle modeled by the equation x + y = 10, at what height from the water's surface will the beam of light hit the dolphin?

Answer 1

you have to write both equations in terms of y and solve for x

y = -0.4x^2 + 3x
y = 10 - x

-0.4x^2 + 3x = 10 - x

^ solve for x, then plug back in and find y

Answer 2

ive done it soo many times, and i just cant get it

Answer 3

move all the variables to one side by adding/subtracting as necessary

-0.4x^2 + 3x = 10 - x

subtracting 10 from both sides gives

-0.4x^2 + 3x - 10 = -x

adding x to both sides gives

-0.4x^2 + 4x - 10 = 0

^ apply the quadratic formula and solve for x

Answer 4

thanks