diff --git a/guide/english/mathematics/complex-fractions/index.md b/guide/english/mathematics/complex-fractions/index.md index 68424bd316..48a5ee0e8e 100644 --- a/guide/english/mathematics/complex-fractions/index.md +++ b/guide/english/mathematics/complex-fractions/index.md @@ -3,13 +3,53 @@ title: Complex Fractions --- ## Complex Fractions -This is a stub. Help our community expand it. - -This quick style guide will help ensure your pull request gets accepted. - - - -#### More Information: - +Complex fractions are fractions that contain fractions in the numerator or denominator, e.g., (1/2)/3 and 1/(2/3) as well as (1/2)/(3/4) are complex fractions. To work with/simplify these fractions there is really only one rule to keep in mind: +``` +(a/b)/(c/d) = (a/b)*(d/c) +``` +when `b`, `c` and `d` are not 0. Namely, dividing by a fraction is the same thing as multiplying by it's [reciprocal](https://en.wikipedia.org/wiki/Multiplicative_inverse). To see this, note that multiplying both sides of our expression above by `c/d` gives +``` +[(a/b)/(c/d)]*(c/d) = (a/b) +``` +one the left, and +``` +[(a/b)*(d/c)]*(c/d) = [(a*d)/(b*c)]*(c/d) + = (a*d*c)/(b*d*c*) = a/b +``` +on the right, so going backwards and dividing `a/b` by `c/d` indeed gives the product `(a/b)*(d/c)`. +Using this, our examples above can be simplified to +``` +(1/2)/3 = (1/2)*(1/3) = 1/6, +1/(2/3) = 1*(3/2) = 3/2, +(1/2)/(3/4) = (1/2)*(4/3) + = 4/6 = 2/3. +``` +This extends to [real numbers](https://en.wikipedia.org/wiki/Real_number), [complex numbers](https://en.wikipedia.org/wiki/Complex_number) and [algebraic expressions](https://en.wikipedia.org/wiki/Algebraic_expression) as well. For example, +``` +(pi/2)/2 = pi/4, +1/(sqrt(2)/2) = 2/sqrt(2) + = 2*sqrt(2)/2 + = sqrt(2). +``` +and +``` +(1 + 1/x^2)/(2x + 2/x^3) = [(x^2 + 1)/x^2]/[(2x^4 + 2)/x^3] + = [(x^2 + 1)/x^2)]*[x^3/(2x^4 + 2)] + = [(x^2 + 1)*x^3]/[x^2*(2x^4 + 2)] + = [(x^2 + 1)*x]/[(2x^4 + 2)]. +``` +Note that in the example above we needed to get the numerator and denominator into a fractional form before being able to use the rule where division by a fraction is equivalent to multiplying by a denominator. Similarly, if we want to simplify +``` +(1 + 1/2)/(2 + 2/3) +``` +we must first simplify this into a fraction divided by another fraction to be able to use our rule above. We have +``` +1 + 1/2 = (2 + 1)/2 = 3/2, +2 + 2/3 = (2*3 + 2)/3 = 8/3, +``` +so we have +``` +(1 + 1/2)/(2 + 2/3) = (3/2)/(8/3) = (3/2)*(3/8) = 9/16. +```