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214 Chapter 3 Exponential and Logarithmic Functions<br />

119.<br />

2x 3 x 2 45x x2x 2 x 45 120.<br />

x2x 9x 5<br />

3x 3 5x 2 12x x3x 2 5x 12<br />

x3x 4x 3<br />

121. f g2 f 2 g2 32 2 2 3 1 8 7 15<br />

122. f g1 1 2 1<br />

123. fg6 f 6g6 36 26 3 1 20215 4300<br />

124. f g 0 2<br />

125.<br />

5x 7 x 4<br />

12<br />

1 2 126. and intersect at x 0.3<br />

y 2x 3<br />

y 8x<br />

The graphs of y 5x 7<br />

and y 2 x 4<br />

intersect when x 2.75<br />

or 11 4 .<br />

−10<br />

−4<br />

12<br />

127.<br />

3x 2 9<br />

The graphs of y 1 3x 2 and y 2 9 intersect<br />

when x 27.667 or 83 3 .<br />

128. y x 11 and y x 2 do not intersect.<br />

No solution<br />

Section 3.3<br />

Properties of Logarithms<br />

■<br />

■<br />

1. (a)<br />

You should know the following properties of logarithms.<br />

(a)<br />

(b)<br />

(c)<br />

log a x log b x<br />

log b a<br />

log a uv log a u log a v<br />

log a uv log a u log a v<br />

lnuv ln u ln v<br />

lnuv ln u ln v<br />

(d) log a u n n log a u<br />

ln u n n ln u<br />

You should be able to rewrite logarithmic expressions using these properties.<br />

Vocabulary Check<br />

1. change-of-base 2.<br />

ln x<br />

ln a<br />

3. log a u n<br />

4. ln u ln v<br />

log 5 x log 10 x<br />

log 10 5<br />

(b) log 5 x ln x<br />

ln 5<br />

2. (a)<br />

log 3 x log 10 x<br />

log 10 3<br />

(b) log 3 x ln x<br />

ln 3<br />

© Houghton Mifflin Company. All rights reserved.

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