Help please. Which of the following answers has simplified the following expression by combining like terms correctly? 6b - 2a + 9 - b + 5a Group of answer choices
A 7a + 7b + 9
B 3a + 5b + 9
C 17ab
D none of these answers are correct

B is the correct answer

Step-by-step explanation:

You have to do 6b- 1b 5b

-2a+5a= 3a

9

Step-by-step explanation:

The wind has a speed of w and a direction α with the vertical.  The x component of that speed is w sin α.  The y component is -w cos α.

In order to stay on the north trajectory AB, the plane must have a horizontal speed of -w sin α.  The plane's speed is v, so using Pythagorean theorem, the y component of the plane's speed is:

v² = (-w sin α)² + vᵧ²

v² = w² sin²α + vᵧ²

vᵧ = √(v² − w² sin²α)

The total vertical speed is therefore √(v² − w² sin²α) − w cos α.

If a is the length of AB, then the time is:

t = a / [√(v² − w² sin²α) − w cos α]

To rationalize the denominator, we multiply by the conjugate.

t = a / [√(v² − w² sin²α) − w cos α] × [√(v² − w² sin²α) + w cos α] / [√(v² − w² sin²α) + w cos α]

t = a [√(v² − w² sin²α) + w cos α] / (v² − w² sin²α − w² cos²α)

t = a [√(v² − w² sin²α) + w cos α] / (v² − w²)