If \(\displaystyle \lim_{x \to 0} \dfrac{e^{ax} - \cos(bx) - \dfrac{cxe^{-cx}}{2}}{1 - \cos(2x)} = 17\), then \(5a^2+b^2\) is equal to:
\( 68 \)
\( 76 \)
\( 64 \)
\( 72 \)