Даю 100 баллов!! Помогите

1a)f(x)=2x4+x3-5, f(x)=8x3+3x2
1b)f(x)= x + sin x, f)(x)=1-cos x
1c)f(x)=1/3x3+x(1/2), f(x)=1/3.(-3).x(-4)+1/2.x(-1/2)=-x(-4)+1/2.x(-1/2)
1d)f(x)=x.cotg x, f(x)=1.cotg x -x/sin2x=cotg x -x/sin2x
2a)f(x) = (-6x+2)(5-x2)=-30x+6x3+10-2x2,f(x)=18x2-4x-30,f(1)=-16
2b)f(x)=x2/(x+5), f(x)=(2x.(x+5)-2x)/(x+5)2=(2x2+8x)/(x+5)2,f(-4)=0
2c)f(x)=(3+x/2)1/2,f(x)=1/2.(3+x/2)(-1/2).1/2=1/4. (3+x/2)(-1/2),f(2)=1/8
3)f(x)=2.cos x + x, f(x)=-2sinx +1,f(x)=0, -2.sinx+1=0, sinx =1/2,x=p/6+2k.p i toe x =5/6p+2k.p
4)f(x)= 2/3.x3-8x, f(x)=2x2-8, g(x)=2.x(1/2),g(x)=2.1/2.x(-1/2)=x(-1/2)
f(x)/g(x)=0, f(x)=0, 2x2-8=0,2x2=8,x2=4, /x/=2