operations on functions. definition. sum, difference, product, quotient and composite functions let...

OPERATIONS ON FUNCTIONS


Definition. Sum, Difference, Product, Quotient and Composite Functions

Let f and g be functions of the variable x.

1. The sum function f+g is the function defined by

xgxfxgf



2. The difference function f – g is the function defined by

xgxfxgf



3. The product function fg is the function defined by

xgxfxfg



4. The quotient function is the function defined by

0

xg,

xg

xfx

g

f

fg–



5. The composite function f g is the function defined by

xgfxgf

O


The domain of f+g , f – g, fg, and

is the intersection of the domains of f and g, with the added restriction on the quotient.

The domain of consists of the set of x’s for which g(x) is contained in the domain of f.

fg–

Of g


Illustration. If and

, then

1xxf

22 xxxg

xgxfxgf.a 1 x 22 xx 12 x

xgxfxgf.b 1 x 22 xx

322 xx



, then

1xxf

22 xxxg

xgxfxfg.c 21 2 xxx

233 xx

xgxf

gf

x.d

221

xx

x

12

1

x,x

211

xx

x



, then

1xxf

22 xxxg

xgfxgf.e

22 xxf

12 xx

122 xx


Illustration. Given and

.

1xxf

22 xxxg

Rf Dom Rg Domand

gfgf DomDomDom RRR

fg,f-g DomDom also iswhich



.

1xxf

22 xxxg

Rf Dom Rg Domand

0

xggf

gf

andDomDomDom

21,xR and

21,R



.

1xxf

22 xxxg

Rf Dom Rg Domand

fxggxxgf DomandDomDom

R



, then

xxf xxg 2

xgxfxgf.a

xx 2

xgxfxgf.b

xx 2



, then

xxf xxg 2

xgxfxfg.c xx 222 xx

xgxf

gf

x.d

x

x

2 x

xx

2

2 2



, then

xxf xxg 2

xgfxgf.e

xf 2

x 2

4 2 x



, then

xxf xxg 2

xfgxfg.f

xg

x 2



.

xxf xxg 2

0 xxfDom 2 xxgDomand

gfgf DomDomDom 20,

fg,f-g DomDom also iswhich



.

xxf xxg 2


0

xggf

gf

andDomDomDom

220 x, and

20,


fxggxxgf DomandDomDom

022 xxx and


.

xxf xxg 2


2 xx


gxffxxfg DomandDomDom

20 xxx and


.

xxf xxg 2


40, 40 xxx and

For numbers 1-5, find

and their respective domains.

TIME TO THINK

211 2 xxgxxf. ;

,fg,gf,gf

121

2

xxgx

xxf. ;

gf,gf and

xxxgx

xf. 41

3 2 ;

For numbers 1-5, find

and their respective domains.

TIME TO THINK

444 xxgxxf. ;

,fg,gf,gf

33 25 xxgxxf. ;

gf,gf and

TIME TO THINK ,xxf. If6

.hgf find ,xxh 3and

,x

xxg

1

,xxgxxgf. andIf 217

.xffind

operations on functions. definition. sum, difference, product, quotient and composite functions let...

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