0/2011 (a)
Prove that cos3x = 4cos'x - 3cos x. Hence, show that
cos2x =-(cos 6x + 3cos 2x).
(b)
[4 marks]
Use the above identity to find all the solutions in the interval
-180° <x<180° of the equation 2 cos 3x + cos2x+1= 0. [7 marks]

Which of the following expressions is equal to 2x^2+8

Girardo is using the model below to solve the equation . girardo uses the following steps: step 1 add 4 negative x-tiles to both sides step 2 add 1 negative unit tile to both sides step 3 the solution is which step could be adjusted so that gerardo's final step results in a positive x-value? in step 1, he should have added 4 positive x-tiles to both sides. in step 1, he should have added 3 negative x-tiles to both sides. in step 2, he should have added 4 negative unit tiles to both sides. in step 2, he should have added 1 positive unit tile to both sides.

If f(x) = 6x – 4, what is f(x) when x = 8? a2 b16 c44 d52