Evaluate the expression

(2/5 + 1) x (6 - 2)

1 2/5 x 4

4 + 8/5

5 3/5

5.6

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a) 0 seconds.

b) The stunt diver is in the air for 2.81 seconds.

Step-by-step explanation:

Solving a quadratic equation:

Given a second order polynomial expressed by the following equation:

.

This polynomial has roots such that , given by the following formulas:

Height of the diver after t seconds:

a) How long is the stunt diver above 15 m?

Quadratic equation with , so the parabola is concave down, and it will be above 15m between the two roots that we found for . So

Quadratic equation with . Then

Negative , which means that the stunt diver is never above 15m, so 0 seconds.

b) How long is the stunt diver in the air?

We have to find how long it takes for the diver to hit the ground, that is, t for which . So

Quadratic equation with . Then

Time is a positive measure, so we take 2.81.

The stunt diver is in the air for 2.81 seconds.