### Home > A2C > Chapter 11 > Lesson 11.2.3 > Problem11-77

11-77.
1. Use the properties of logarithms to rewrite each equation and then solve. Check for extraneous roots. Homework Help ✎

1. log(x) + log(x + 21) = 2

2. 2log4(x) − log4(3) = 2

3. log2(9x + 5) − log2(x2 − 1) = 2

4. log7(x + 1) + log7(x − 5) = 1

log(x2 + 21x) = 2

x2 + 21x = 102

(x − 4)(x + 25) = 0

4

$\text{log}_4\left(\frac{x^2}{3}\right)=2$

$\text{log}_2 \left(\frac{9x+2}{x^{2}-1}\right)=2$

3

See parts (a) and (b).