Hi there!

We can begin by multiplying by its conjugate:

Simplify using the identity:


Take the square root of the expression:

Multiply again by the conjugate to get a SINGLE term in the denominator:

Simplify:

Use the above trig identity one more:

Cancel out sinA:

Split the fraction into two:

Recall:

Simplify:

Answer:
the answer would be:

Hope that helps! :)
Step-by-step explanation:
You might be able to do direct substitution.
(f-g)(x) will be 3x^2 -2x+4 -(5x^2+6×-8)
distribute the -sign, gives us
3x^2-2x+4-5x^2-6x+8,
now combine like terms and should get,
-2x^2-8x+12,
final answer,
(f-g)(x)= -2x^2-8x+1×,
hope it helped,
good luck
Using a calculator can help. You get 0.625, or 5/8.