Question 366198
1a){{{dy/dx=3x^2-12x+highlight(9)}}}
b) Correct!
c) Correct!
d) Correct!
e){{{dy/dx=3*sinh(x)+4*sinh(x)}}}
I think you misinterpreted as {{{sin(hx)}}} when it's actually the hyperbolic sine function, {{{sinh(x)}}}, same for the cosine.
f){{{dy/dx=(x^2+1)cosh(x)+(2x)sinh(x)}}}
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2a) Correct! Could be simplified to {{{dy/dx=e^x(x+2)}}} 
b) Correct!
c) Correct! Could be simplified to {{{dy/dx=4x^3(ln(x)+1)}}}
d) Correct!
e) Correct! Could be simplified to {{{dy/dx=-e^(-x)(cos(x) +sin(x))}}}
f) Correct! but why weren't your answers for 1f and 2f the same??
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3a) {{{dy/dx=(1+e^(-x))cos(x)-sin(x)(-e^(-x))/(1+e^(-x))^2}}}
{{{dy/dx=((1+e^(-x))cos(x)+e^(-x)sin(x))/(1+e^(-x))^2}}}

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b) {{{dy/dx= ((1+x^2)(1/x)-ln(x)(2x))/(1+x^2)^2}}}
{{{dy/dx= ((1+x^2)-2x^2ln(x))/(x(1+x^2)^2)}}}
{{{dy/dx=(x^2-2x^2ln(x)+1)/(x(x^2+1)^2)}}}