Your answer should be 120
Combine like terms to get 2x + 6x which is 8x and 3y + 9y which is 12y so the simplified answer is 8x + 12y
Recall the Maclaurin expansion for cos(x), valid for all real x :

Then replacing x with √5 x (I'm assuming you mean √5 times x, and not √(5x)) gives

The first 3 terms of the series are

and the general n-th term is as shown in the series.
In case you did mean cos(√(5x)), we would instead end up with

which amounts to replacing the x with √x in the expansion of cos(√5 x) :

Answer:
The answer to your question is: 2, 4, 5, 1 , 3
Step-by-step explanation:
The first line is the second
(3x² - 6)² - (3x²)² = 36(1 - x)(1 + 1)
The second line is the forth
9x⁴ - 36x² + 36x² - 9x⁴ = 36(1 - x)(1 + x)
The next line is the fifth
36 - 36x² = 36(1 - x)(1 + x)
The next line is the first
36(1 - x²) = 36(1 - x)(1 + x)
The last line is the third
36(1 - x)(1 + x) = 36(1 - x)(1 + x)