Evaluate
Differentiate w.r.t. z

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\frac{\left(2z^{1}-4\right)\frac{\mathrm{d}}{\mathrm{d}z}(z^{1}+3)-\left(z^{1}+3\right)\frac{\mathrm{d}}{\mathrm{d}z}(2z^{1}-4)}{\left(2z^{1}-4\right)^{2}}
For any two differentiable functions, the derivative of the quotient of two functions is the denominator times the derivative of the numerator minus the numerator times the derivative of the denominator, all divided by the denominator squared.
\frac{\left(2z^{1}-4\right)z^{1-1}-\left(z^{1}+3\right)\times 2z^{1-1}}{\left(2z^{1}-4\right)^{2}}
The derivative of a polynomial is the sum of the derivatives of its terms. The derivative of a constant term is 0. The derivative of ax^{n} is nax^{n-1}.
\frac{\left(2z^{1}-4\right)z^{0}-\left(z^{1}+3\right)\times 2z^{0}}{\left(2z^{1}-4\right)^{2}}
Do the arithmetic.
\frac{2z^{1}z^{0}-4z^{0}-\left(z^{1}\times 2z^{0}+3\times 2z^{0}\right)}{\left(2z^{1}-4\right)^{2}}
Expand using distributive property.
\frac{2z^{1}-4z^{0}-\left(2z^{1}+3\times 2z^{0}\right)}{\left(2z^{1}-4\right)^{2}}
To multiply powers of the same base, add their exponents.
\frac{2z^{1}-4z^{0}-\left(2z^{1}+6z^{0}\right)}{\left(2z^{1}-4\right)^{2}}
Do the arithmetic.
\frac{2z^{1}-4z^{0}-2z^{1}-6z^{0}}{\left(2z^{1}-4\right)^{2}}
Remove unnecessary parentheses.
\frac{\left(2-2\right)z^{1}+\left(-4-6\right)z^{0}}{\left(2z^{1}-4\right)^{2}}
Combine like terms.
\frac{-10z^{0}}{\left(2z^{1}-4\right)^{2}}
Subtract 2 from 2 and 6 from -4.
\frac{-10z^{0}}{\left(2z-4\right)^{2}}
For any term t, t^{1}=t.
\frac{-10}{\left(2z-4\right)^{2}}
For any term t except 0, t^{0}=1.