The Fourier series of the function f (x) = 2x² defined on [-7, n] is given by 272 + 3 00 Σ 8(-1)" -cos nx. n? n=1 The sum of the series > n4 n=1

I need help with these: a) Find the Fourier series of f(x) = |x| where −L < x < L. b) What is the Fourier series of the function f of period 2L defined byf(x) = -1 if −L < x< 0,f(x) = 1 if 0 < x < L,What does the series converge to when x = 0?

Only do number 1