5. 2.9n+1.7=3.5+2.3n
.6n+1.7=3.5
.6n=1.8
n=3
6. -4-5(x+8)
-4-5x-40
-5x-44
sin θ = 3 / 7 = .429
sin^2 θ + cos^2 θ = 1 trig identity
9/49 + cos^2 θ = 1
cos^2 θ = 40 / 49 = .816 cos θ = .903
Check .429^2 + .903^2 = 1
cos .903 = 25.4 deg
In the second quadrant sin = +, cos = -, tan = -
So 25.4 deg in the second quadrant = 180 - 25.4 = 154.6 deg
Check:
sin 154.6 = .428
cos 154.6 = -.903
tan 154.6 = -.475
<h2>
Hello!</h2>
The answers are:
a) 
b) 
<h2>Why?</h2>
First, we need to know that for this case:

So,


We must add
to the expression in order to form a perfect square trinomial,

Writing the trinomial as a binomial square:

Have a nice day!