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  2. Cubic equation - Wikipedia

    en.wikipedia.org/wiki/Cubic_equation

    If only one root, say r 1, is real, then r 2 and r 3 are complex conjugates, which implies that r 2 – r 3 is a purely imaginary number, and thus that (r 2 – r 3) 2 is real and negative. On the other hand, r 1 – r 2 and r 1 – r 3 are complex conjugates, and their product is real and positive. [ 23 ]

  3. Euler substitution - Wikipedia

    en.wikipedia.org/wiki/Euler_substitution

    The substitutions of Euler can be generalized by allowing the use of imaginary numbers. For example, in the integral +, the substitution + = + can be used. Extensions to the complex numbers allows us to use every type of Euler substitution regardless of the coefficients on the quadratic.

  4. Plus and minus signs - Wikipedia

    en.wikipedia.org/wiki/Plus_and_minus_signs

    When placed after special sets of numbers, plus and minus signs are used to indicate that only positive numbers and negative numbers are included, respectively. For example, + is the set of all positive integers and is the set of all negative integers. In these cases, a subscript 0 may also be added to clarify that 0 is included.

  5. Ka/Ks ratio - Wikipedia

    en.wikipedia.org/wiki/Ka/Ks_ratio

    Approximate methods involve three basic steps: (1) counting the number of synonymous and nonsynonymous sites in the two sequences, or estimating this number by multiplying the sequence length by the proportion of each class of substitution; (2) counting the number of synonymous and nonsynonymous substitutions; and (3) correcting for multiple ...

  6. Indifference curve - Wikipedia

    en.wikipedia.org/wiki/Indifference_curve

    The curves are convex to the origin, describing the negative substitution effect. As price rises for a fixed money income, the consumer seeks the less expensive substitute at a lower indifference curve. The substitution effect is reinforced through the income effect of lower real income (Beattie-LaFrance).

  7. Negative number - Wikipedia

    en.wikipedia.org/wiki/Negative_number

    In mathematics, a negative number is the opposite of a positive real number. [1] Equivalently, a negative number is a real number that is less than zero. Negative numbers are often used to represent the magnitude of a loss or deficiency. A debt that is owed may be thought of as a negative asset.

  8. Additive inverse - Wikipedia

    en.wikipedia.org/wiki/Additive_inverse

    In elementary mathematics, the additive inverse is often referred to as the opposite number, [3] [4] or its negative. [5] The unary operation of arithmetic negation [6] is closely related to subtraction [7] and is important in solving algebraic equations. [8] Not all sets where addition is defined have an additive inverse, such as the natural ...

  9. Integration by substitution - Wikipedia

    en.wikipedia.org/wiki/Integration_by_substitution

    In calculus, integration by substitution, also known as u-substitution, reverse chain rule or change of variables, [1] is a method for evaluating integrals and antiderivatives. It is the counterpart to the chain rule for differentiation , and can loosely be thought of as using the chain rule "backwards."