We have,
=ddxx4(5 sin x−3 cos x)
=5ddxx4 5 sin x−3 x4 cos x
=5ddx(x4 sin x)−3ddx(x4 cos x)
=5(sin xddx(x4)+x4ddx(sinx))−3(cos xddx(x4)+x4 ddx(cos x)) [Apply product rule]
=5(sin x×4x3+x4×cos x)−3(cos x×4x3+x4(−sin x))
=20x3×sin x+5x4 cos x−12x3 cos x+3x4 sin x