Solve (3/x+4+6x/x^2+x-12-1/x-3

$$( \frac{ 3 }{ x+4 } + \frac{ 6x }{ { x }^{ 2 } +x-12 } - \frac{ 1 }{ x-3 }$$

Evaluate

$$\frac{8x-13}{\left(x-3\right)\left(x+4\right)}$$

Short Solution Steps

Factor x^{2}+x-12.

$$\frac{3}{x+4}+\frac{6x}{\left(x-3\right)\left(x+4\right)}-\frac{1}{x-3}$$

To add or subtract expressions, expand them to make their denominators the same. Least common multiple of x+4 and \left(x-3\right)\left(x+4\right) is \left(x-3\right)\left(x+4\right). Multiply \frac{3}{x+4} times \frac{x-3}{x-3}.

$$\frac{3\left(x-3\right)}{\left(x-3\right)\left(x+4\right)}+\frac{6x}{\left(x-3\right)\left(x+4\right)}-\frac{1}{x-3}$$

Since \frac{3\left(x-3\right)}{\left(x-3\right)\left(x+4\right)} and \frac{6x}{\left(x-3\right)\left(x+4\right)} have the same denominator, add them by adding their numerators.

$$\frac{3\left(x-3\right)+6x}{\left(x-3\right)\left(x+4\right)}-\frac{1}{x-3}$$

Do the multiplications in 3\left(x-3\right)+6x.

$$\frac{3x-9+6x}{\left(x-3\right)\left(x+4\right)}-\frac{1}{x-3}$$

Combine like terms in 3x-9+6x.

$$\frac{9x-9}{\left(x-3\right)\left(x+4\right)}-\frac{1}{x-3}$$

To add or subtract expressions, expand them to make their denominators the same. Least common multiple of \left(x-3\right)\left(x+4\right) and x-3 is \left(x-3\right)\left(x+4\right). Multiply \frac{1}{x-3} times \frac{x+4}{x+4}.

$$\frac{9x-9}{\left(x-3\right)\left(x+4\right)}-\frac{x+4}{\left(x-3\right)\left(x+4\right)}$$

Since \frac{9x-9}{\left(x-3\right)\left(x+4\right)} and \frac{x+4}{\left(x-3\right)\left(x+4\right)} have the same denominator, subtract them by subtracting their numerators.

$$\frac{9x-9-\left(x+4\right)}{\left(x-3\right)\left(x+4\right)}$$

Do the multiplications in 9x-9-\left(x+4\right).

$$\frac{9x-9-x-4}{\left(x-3\right)\left(x+4\right)}$$

Combine like terms in 9x-9-x-4.

$$\frac{8x-13}{\left(x-3\right)\left(x+4\right)}$$

Expand \left(x-3\right)\left(x+4\right).

$$\frac{8x-13}{x^{2}+x-12}$$

Differentiate w.r.t. x

$$\frac{-8x^{2}+26x-83}{\left(\left(x-3\right)\left(x+4\right)\right)^{2}}$$

Steps Using Derivative Rule for Quotient

Factor x^{2}+x-12.

$$\frac{\mathrm{d}}{\mathrm{d}x}(\frac{3}{x+4}+\frac{6x}{\left(x-3\right)\left(x+4\right)}-\frac{1}{x-3})$$

To add or subtract expressions, expand them to make their denominators the same. Least common multiple of x+4 and \left(x-3\right)\left(x+4\right) is \left(x-3\right)\left(x+4\right). Multiply \frac{3}{x+4} times \frac{x-3}{x-3}.

$$\frac{\mathrm{d}}{\mathrm{d}x}(\frac{3\left(x-3\right)}{\left(x-3\right)\left(x+4\right)}+\frac{6x}{\left(x-3\right)\left(x+4\right)}-\frac{1}{x-3})$$

Since \frac{3\left(x-3\right)}{\left(x-3\right)\left(x+4\right)} and \frac{6x}{\left(x-3\right)\left(x+4\right)} have the same denominator, add them by adding their numerators.

$$\frac{\mathrm{d}}{\mathrm{d}x}(\frac{3\left(x-3\right)+6x}{\left(x-3\right)\left(x+4\right)}-\frac{1}{x-3})$$

Do the multiplications in 3\left(x-3\right)+6x.

$$\frac{\mathrm{d}}{\mathrm{d}x}(\frac{3x-9+6x}{\left(x-3\right)\left(x+4\right)}-\frac{1}{x-3})$$

Combine like terms in 3x-9+6x.

$$\frac{\mathrm{d}}{\mathrm{d}x}(\frac{9x-9}{\left(x-3\right)\left(x+4\right)}-\frac{1}{x-3})$$

To add or subtract expressions, expand them to make their denominators the same. Least common multiple of \left(x-3\right)\left(x+4\right) and x-3 is \left(x-3\right)\left(x+4\right). Multiply \frac{1}{x-3} times \frac{x+4}{x+4}.

$$\frac{\mathrm{d}}{\mathrm{d}x}(\frac{9x-9}{\left(x-3\right)\left(x+4\right)}-\frac{x+4}{\left(x-3\right)\left(x+4\right)})$$

Since \frac{9x-9}{\left(x-3\right)\left(x+4\right)} and \frac{x+4}{\left(x-3\right)\left(x+4\right)} have the same denominator, subtract them by subtracting their numerators.

$$\frac{\mathrm{d}}{\mathrm{d}x}(\frac{9x-9-\left(x+4\right)}{\left(x-3\right)\left(x+4\right)})$$

Do the multiplications in 9x-9-\left(x+4\right).

$$\frac{\mathrm{d}}{\mathrm{d}x}(\frac{9x-9-x-4}{\left(x-3\right)\left(x+4\right)})$$

Combine like terms in 9x-9-x-4.

$$\frac{\mathrm{d}}{\mathrm{d}x}(\frac{8x-13}{\left(x-3\right)\left(x+4\right)})$$

Use the distributive property to multiply x-3 by x+4 and combine like terms.

$$\frac{\mathrm{d}}{\mathrm{d}x}(\frac{8x-13}{x^{2}+x-12})$$

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.

$$\frac{\left(x^{2}+x^{1}-12\right)\frac{\mathrm{d}}{\mathrm{d}x}(8x^{1}-13)-\left(8x^{1}-13\right)\frac{\mathrm{d}}{\mathrm{d}x}(x^{2}+x^{1}-12)}{\left(x^{2}+x^{1}-12\right)^{2}}$$

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}.

$$\frac{\left(x^{2}+x^{1}-12\right)\times 8x^{1-1}-\left(8x^{1}-13\right)\left(2x^{2-1}+x^{1-1}\right)}{\left(x^{2}+x^{1}-12\right)^{2}}$$

Simplify.

$$\frac{\left(x^{2}+x^{1}-12\right)\times 8x^{0}-\left(8x^{1}-13\right)\left(2x^{1}+x^{0}\right)}{\left(x^{2}+x^{1}-12\right)^{2}}$$

Multiply x^{2}+x^{1}-12 times 8x^{0}.

$$\frac{x^{2}\times 8x^{0}+x^{1}\times 8x^{0}-12\times 8x^{0}-\left(8x^{1}-13\right)\left(2x^{1}+x^{0}\right)}{\left(x^{2}+x^{1}-12\right)^{2}}$$

Multiply 8x^{1}-13 times 2x^{1}+x^{0}.

$$\frac{x^{2}\times 8x^{0}+x^{1}\times 8x^{0}-12\times 8x^{0}-\left(8x^{1}\times 2x^{1}+8x^{1}x^{0}-13\times 2x^{1}-13x^{0}\right)}{\left(x^{2}+x^{1}-12\right)^{2}}$$

To multiply powers of the same base, add their exponents.

$$\frac{8x^{2}+8x^{1}-12\times 8x^{0}-\left(8\times 2x^{1+1}+8x^{1}-13\times 2x^{1}-13x^{0}\right)}{\left(x^{2}+x^{1}-12\right)^{2}}$$

Simplify.

$$\frac{8x^{2}+8x^{1}-96x^{0}-\left(16x^{2}+8x^{1}-26x^{1}-13x^{0}\right)}{\left(x^{2}+x^{1}-12\right)^{2}}$$

Combine like terms.

$$\frac{-8x^{2}+26x^{1}-83x^{0}}{\left(x^{2}+x^{1}-12\right)^{2}}$$

For any term t, t^{1}=t.

$$\frac{-8x^{2}+26x-83x^{0}}{\left(x^{2}+x-12\right)^{2}}$$

For any term t except 0, t^{0}=1.

$$\frac{-8x^{2}+26x-83}{\left(x^{2}+x-12\right)^{2}}$$