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?

a)2.7 feet

b)3 feet

c)5 feet

d)5.6 feet

We can find the answer by solving the two equations simultaneously.

equation 1: y = -0.4x^2 +3xequation 2: x + y = 10
We need to write equation to with y as the subject:equation 2: y = 10 - x

equation 1 = equation 2:
10 - x = -0.4x^2 + 3x0.4x^2 - 4x + 10 = 02x^2 - 20 + 50 = 0(2x - 10)(x - 5) = 0x = -10/2 or x = 5

But x >= 0 (the question says it's a height above the water), so x = 5

Substituting x = 5 into one of the equations:
y = 10 - x
y = 10 - 5
y = 5

So the answer is C