Conjugate

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In the conjugate of a binomium the second term is negativ. For the real numbers a and b you write the conjugate of a + b as a – b.

To solve a multiplication with it, you must calculate this term-by-term

(a + b) (a − b) = a² − ab + ab − b² = a² − b²

It is a binomial formula, and is frequently used to simplify calculations.

By multiplication of the numerator and denominator of a fraction by the same conjugate you can elimate roots in the numerator