Problem

Simplify ((4x-16)/(5x+15))/((4-x)/(2x+6))

The problem you have presented is a question of algebraic simplification involving rational expressions. Specifically, you are asked to simplify a complex fraction where the numerator and denominator are themselves fractions involving polynomials. The solution would involve factoring where possible, identifying and canceling common factors between the numerators and denominators, and applying the division rule for fractions, which states that dividing by a fraction is equivalent to multiplying by its reciprocal.

$\frac{\frac{4 x - 16}{5 x + 15}}{\frac{4 - x}{2 x + 6}}$

Answer

Expert–verified

Solution:

Step:1

Take the inverse of the denominator and multiply it with the numerator: $\frac{4x - 16}{5x + 15} \cdot \frac{2x + 6}{4 - x}$

Step:2

Begin simplification process.

Step:2.1

Extract the common factor from the first term in the numerator.

Step:2.1.1

Pull out the common factor from $4x$: $\frac{4(x) - 16}{5x + 15} \cdot \frac{2x + 6}{4 - x}$

Step:2.1.2

Extract the common factor from $-16$: $\frac{4x - 4 \cdot 4}{5x + 15} \cdot \frac{2x + 6}{4 - x}$

Step:2.1.3

Combine the factored terms: $\frac{4(x - 4)}{5x + 15} \cdot \frac{2x + 6}{4 - x}$

Step:2.2

Identify and factor out the common factor from the first term in the denominator.

Step:2.2.1

Isolate the common factor from $5x$: $\frac{4(x - 4)}{5(x) + 15} \cdot \frac{2x + 6}{4 - x}$

Step:2.2.2

Pull out the common factor from $15$: $\frac{4(x - 4)}{5x + 5 \cdot 3} \cdot \frac{2x + 6}{4 - x}$

Step:2.2.3

Consolidate the factored terms: $\frac{4(x - 4)}{5(x + 3)} \cdot \frac{2x + 6}{4 - x}$

Step:2.3

Extract the common factor from the second term in the numerator.

Step:2.3.1

Isolate the common factor from $2x$: $\frac{4(x - 4)}{5(x + 3)} \cdot \frac{2(x) + 6}{4 - x}$

Step:2.3.2

Extract the common factor from $6$: $\frac{4(x - 4)}{5(x + 3)} \cdot \frac{2x + 2 \cdot 3}{4 - x}$

Step:2.3.3

Combine the factored terms: $\frac{4(x - 4)}{5(x + 3)} \cdot \frac{2(x + 3)}{4 - x}$

Step:2.4

Eliminate the common factor between the numerator and the denominator.

Step:2.4.1

Factor out $(x + 3)$ from the denominator: $\frac{4(x - 4)}{(x + 3) \cdot 5} \cdot \frac{2(x + 3)}{4 - x}$

Step:2.4.2

Factor out $(x + 3)$ from the numerator: $\frac{4(x - 4)}{(x + 3) \cdot 5} \cdot \frac{(x + 3) \cdot 2}{4 - x}$

Step:2.4.3

Cancel out the common $(x + 3)$ factor: $\frac{4(x - 4)}{(\cancel{x + 3}) \cdot 5} \cdot \frac{(\cancel{x + 3}) \cdot 2}{4 - x}$

Step:2.4.4

Simplify the expression: $\frac{4(x - 4)}{5} \cdot \frac{2}{4 - x}$

Step:2.5

Perform the multiplication of the simplified fractions: $\frac{4(x - 4) \cdot 2}{5(4 - x)}$

Step:2.6

Multiply the constants: $\frac{8(x - 4)}{5(4 - x)}$

Step:2.7

Simplify by canceling out the common factor $(x - 4)$ and $(4 - x)$.

Step:2.7.1

Factor out $-1$ from $x$: $\frac{8(-1(-x) - 4)}{5(4 - x)}$

Step:2.7.2

Express $-4$ as $-1(4)$: $\frac{8(-1(-x) - 1(4))}{5(4 - x)}$

Step:2.7.3

Factor out $-1$ from the expression: $\frac{8(-1(-x + 4))}{5(4 - x)}$

Step:2.7.4

Rearrange the terms: $\frac{8(-1(-x + 4))}{5(-x + 4)}$

Step:2.7.5

Cancel out the common factor: $\frac{8(-1(\cancel{-x + 4}))}{5(\cancel{-x + 4})}$

Step:2.7.6

Finalize the expression: $\frac{8 \cdot (-1)}{5}$

Step:3

Multiply the constants: $\frac{-8}{5}$

Step:4

Place the negative sign in front of the fraction: $-\frac{8}{5}$

Step:5

Present the result in various forms:

Exact Form: $-\frac{8}{5}$ Decimal Form: $-1.6$ Mixed Number Form: $-1\frac{3}{5}$

Knowledge Notes:

The problem involves simplifying a complex fraction by performing operations such as factoring, multiplying by the reciprocal, and canceling common factors. Here are the relevant knowledge points:

  1. Multiplying by the Reciprocal: When dividing fractions, multiply by the reciprocal of the divisor.

  2. Factoring: Extract common factors from terms to simplify expressions.

  3. Canceling Common Factors: When a factor appears in both the numerator and the denominator, it can be canceled out.

  4. Negative Numbers: Factoring out $-1$ can help in simplifying expressions with negative terms.

  5. Simplifying Complex Fractions: Complex fractions can be simplified by performing multiplication and cancellation step by step.

  6. Representation of Rational Numbers: Rational numbers can be represented in exact form, decimal form, and mixed number form.

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