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can someone plz help me w/ these q's? 1. a series has the nth term given by Tn=n^3 -5. find the sum of 4 terms. 2. the sum of n terms of 214+206+198+... is 2760. evaluate n. 3. evaluate: 7 (sigma) 1/n 3 as a fraction. ==============================================...

I have a problem with these questions; if anyone knows how to do it I would be very grateful!! 1) If the sum of two roots of x (to the power 4) + 2x (to the power 3) - 8x (squared) - 18x - 9=0 is 0, find the roots of the equation. 2) Solve 2cos (cubed)x + cos (squared) x - cosx =0 for x is...