42 is the answer
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Option A

<em><u>Solution:</u></em>
Given that we have to rewrite with only sin x and cos x
Given is cos 3x

We know that,

Therefore,
---- eqn 1
We know that,


Substituting these values in eqn 1
-------- eqn 2
We know that,

Applying this in above eqn 2, we get



Therefore,

Option A is correct
Answer:
2nd option
Step-by-step explanation:
Given
3x³ - 15x² - 4x + 20
step 1 ( group the first/second and third/fourth terms )
(3x³ - 15x² ) + (- 4x + 20)
step 2 ( factor each group )
3x² (x - 5) - 4(x - 5) ← note factor of - 4 ( not + 4 )
step 3 ( factor out (x - 5) from each term )
(x - 5)(3x² - 4)
3:5
1:1
1.5 or 1:5 not sure