Domain
The set of all real numbers for which a rational expression is defined. Also, the set of first components in the ordered pair set.
Divisor
The number by which another number is divided.
Division property of inequalities
Divide each side by a positive quantity. If \(a < b\) and c is positive, then \(\frac{a}{c} < \frac{b}{c}\). Divide each side by a negative quantity and reverse the inequality symbol. If \(a < b\) and c is negative, then \(\frac{a}{c} > \frac{b}{c}\).
Dividing one integer from another
Let $a$ and $b$ be integers. \(\frac{0}{a} = 0\), \(a \ne 0\). \(\frac{a}{0}\) is undefined. Like signs: \(\frac{a}{b} > 0\), \(b \ne 0\). Unlike signs: \(\frac{a}{b} < 0\), \(b \ne 0\).
Dividing rational expressions
Let $a$, $b$, $c$, and $d$ represent real numbers, variables, or algebraic expressions such that \(b \ne 0\), \(c \ne 0\), and \(d \ne 0\). Then the quotient of $\frac{a}{b}$ and $\frac{c}{d}$ is $\frac{a}{b} \div \frac{c}{d} = \frac{a}{b}•\frac{d}{c} = \frac{{ad}}{{bc}}$.
Dividing a polynomial by a monomial
Let $a$, $b$, and $c$ be real numbers, variables, or algebraic expressions, such that \(c \ne 0\). \(1.{\rm{ }}\frac{{a + b}}{c} = \frac{a}{c} + \frac{b}{c}\)
\(2.{\rm{ }}\frac{{a – b}}{c} = \frac{a}{c} – \frac{b}{c}\)
Dividing fractions
Let $a$, $b$, $c$, and $d$ be integers with \(b \ne 0\), \(c \ne 0\), and \(d \ne 0\). Then the quotient of $\frac{a}{b}$ and $\frac{c}{d}$ is $\frac{a}{b} \div \frac{c}{d} = \frac{a}{b}•\frac{d}{c}$.
Dividend
The number that is being divided by another number.
Distributive property
Multiplication distributes over addition.
\(a(b + c) = ab + ac{\rm{ }}(a + b)c = ac + bc\)
Distance formula
The distance $d$ between the two points $\left( {{x_1},{y_1}} \right)$ and $\left( {{x_2},{y_2}} \right)$ in a coordinate plane is $d = \sqrt {{{\left( {{x_2} – {x_1}} \right)}^2} + {{\left( {{y_2} – {y_1}} \right)}^2}} $.
Discriminant
The expression inside the radical of the Quadratic Formula, ${b^2} – 4ac$. 1. If ${b^2} – 4ac > 0$, the equation has two real solutions. 2. If ${b^2} – 4ac = 0$, the equation has one repeated real solution. 3. If ${b^2} – 4ac < 0$, the equation has no real solution.
Discount rate
When the discount is given as a percent of the original price.
Discount
The difference between the price a store pays for an item and the price they sell the item for.
Difference of two squares
Let $a$ and $b$ be real numbers, variables, of algebraic expressions. \({a^2} – {b^2} = \left( {a + b} \right)\left( {a – b} \right)\)
Difference
The result of subtracting one integer from another.
Dependent system
A system of equations with infinitely many solutions. Also, the slopes of the lines are equal because the lines are equal.
Denominator
The number below the fraction bar in a fraction.
Decision digit
When rounding a decimal, the decision digit is the digit in the first position you discard.
Dependent variable
The output of a function.