For any rational numbers k, l with kl(l −1) ̸= 0, we prove the generalized Hyers–Ulam stability of the Euler-Lagrange quadratic functional equation f(kx + ly) + f(kx − ly) + 2(l − 1)[k²f(x) − lf(y)] = l[f(kx + y) + f(kx − y)] using both the direct method and fixed point method in fuzzy Banach spaces.