Rewrite

so that it involves only the first power of cosine

All you need is the double angle identity:

So we have

Apply the identity again to the squared term:

it is true

step-by-step explanation:

all the combinations add up i used   calculator

b. y = 4x - 2

step-by-step explanation:

to find a parallel equation to an equation, make sure both equations have the same slope but different y-intercepts.

y = 4x + 1

4 = slope

1 = y-intercept

y = 4x - 2

4 = slope

-2 = y-intercept

they both have the same slope but different y-intercepts, so, b. is the correct answer.

and to check your work, you can graph both equations. : )