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082-Engineering-Mathematics-Anthony-Croft-Robert-Davison-Martin-Hargreaves-James-Flint-Edisi-5-2017

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2.4 Review of some common engineering functions and techniques 71

wherex,zandt are independent variables. It is common practice to contract the term

polynomial expression to polynomial. By convention, a polynomial is usually written

with the powers either increasing or decreasing. For example,

3x+9x 2 −x 3 +2

would be writtenas either

−x 3 +9x 2 +3x+2 or 2+3x+9x 2 −x 3

Thedegreeofapolynomialorpolynomialfunctionisthevalueofthehighestpower.

Equation(2.4)hasdegree2,Equation(2.5)hasdegree4,Equation(2.6)hasdegree1and

Equation(2.7)hasdegree0.Equation(2.3)hasdegreen.Polynomialswithlowdegrees

have special names (seeTable 2.1).

Table2.1

Polynomial Degree Name

ax 4 +bx 3 +cx 2 +dx +e 4 Quartic

ax 3 +bx 2 +cx +d 3 Cubic

ax 2 +bx +c 2 Quadratic

ax +b 1 Linear

a 0 Constant

Typical graphs of some polynomial functions are shown inFigure 2.17.

P(x)

Degree 2

Degree 3

x

Degree 0

Degree 1

Figure2.17

Some typical polynomials.

Engineeringapplication2.4

Ohm’slaw

RecallfromEngineeringapplication1.1thatthecurrentflowingthrougharesistoris

related tothe voltage applied across itby Ohm’s law. The equation is

V=IR

whereV = voltage across the resistor;

I = currentthrough the resistor;

R = resistance value of the resistor,which isaconstant

foragiven temperature.

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