Assignment Help Needed Exponents and Logarithms

If anyone could help me with any of these questions, that would be awesome.

Thanks in advance.

7. Express the function y = 5^x as an equivalent function with base 3.

8. Suppose money can be invested at 3.75% compunded semi-annually. Determine how long it takes for a principal to triple in value.

9. The decibel (dB) is used to measure the loudness of a sound. The equation D = 10log*I* models the decibel level of a sound whose intensity is *I* watts per square metre (W/m^2). The decibel levels of a subway train and normal conversation are 115 dB and 60 dB, respectively. How many times as intense as normal conversation is the noise of a subway train?

10. (a) solve the equation (2^x)^2 - 4(2^x) + 3 = 0

(b) Graph the function y = 2^2x - 4(2^x) + 3

(c) How is the graph in part (b) related to your answer in part (a)?

(d) Describe the graph in part (b). Explain why it has shape.

11. Prove logab = (logcb) / (logca). Hint: let x = logab, y = logcb, and z = logca.