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AQA · 8365
Increasing function
A function whose y-value rises as x increases over an interval. A positive derivative, dydx>0\frac{dy}{dx}>0dxdy>, indicates increasing behaviour.
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Index
The power to which a base is raised. For a positive integer index, it counts repeated factors: x3=x×x×xx^3=x\times x\times xx3=x×x×x. Also called an exponent.
Inequality
A mathematical statement comparing expressions using <<<, >>>, ≤\leq≤ or ≥\geq≥.
Inner function
The function applied first in a nested expression. In f(g(x))f(g(x))f(g(x)), the inner function is ggg.
Input
The value put into a function; in f(x)f(x)f(x), the input is xxx.
Integer
A whole number, including negative whole numbers and zero: for example, −3-3−3, 000 and 777.
Intercept
A point where a graph meets a coordinate axis. At an xxx-intercept, y=0y=0y=0; at a yyy-intercept, x=0x=0x=0.
Interior angle
An angle inside a polygon, between two sides meeting at a vertex.
Interval
A continuous range of values, such as 0<x<10<x<10<x<1.
Inverse function
A function that reverses another function, returning each output to its original input. The inverse of fff is written f−1f^{-1}f−1.
Inverse operation
An operation that reverses another operation, such as division reversing multiplication.
Inverse proportion
A relationship in which the product of two quantities is constant: xy=kxy=kxy=k, or y=kxy=\frac{k}{x}y=xk.
Inverse trigonometric function
A function used to find an angle from a trigonometric value, such as sin−1(0.5)=30∘\sin^{-1}(0.5)=30^\circsin−1(0.5)=30∘. The notation sin−1\sin^{-1}sin−1 does not mean 1/sin1/\sin1/sin.
Like surds
Terms with the same surd part after simplification, such as 353\sqrt{5}35 and 858\sqrt{5}85.
Like terms
Terms with exactly the same variables raised to exactly the same powers, such as 3x2y3x^2y3x2y and −7x2y-7x^2y−7x2y.
Limiting value
A number that the terms of a sequence approach arbitrarily closely and remain close to as the term number increases without bound.
Linear equation
An equation in which each unknown appears only to the first power, with no products of unknowns; for example, 2x−5y+4z=222x-5y+4z=222x−5y+4z=22.
Linear factor
A degree-one expression, such as x−2x-2x−2 or 2x−32x-32x−3, which multiplies another polynomial to give the original polynomial exactly.
Linear inequality
An inequality in which the variable has highest power one, such as 3x+4≥73x+4\geq73x+4≥7.
Linear sequence
A sequence with a constant difference between consecutive terms; also called an arithmetic sequence.
Line segment
The part of a straight line between two endpoints.
Local maximum
A point whose y-coordinate is greater than those of nearby points on either side.
Local minimum
A point whose y-coordinate is smaller than those of nearby points on either side.
Lowest common denominator
The simplest common multiple of the denominators, containing each required factor to its highest power.
Matrix
A rectangular array of numbers or letters arranged in rows and columns.
Maximum value
The greatest value a function actually reaches over the domain being considered.
Midpoint
The point halfway along a line segment, at equal distances from its endpoints. It divides the segment in the ratio 1:11:11:1.
Minimum value
The least value a function actually reaches over the domain being considered.
Multiple
A number that can be written as kqkqkq, where qqq is an integer. For example, 202020 is a multiple of 444 because 20=4×520=4\times520=4×5.
Negative index
A power representing a reciprocal: for example, x−3=1x3x^{-3}=\frac{1}{x^3}x−3=x31, with x≠0x\ne0x=0.
232 key terms