Question

Which equation(s) have x = –3 as the solution? log3(2x + 15) = 2 log5(8x + 9) = 2 log4(–20x + 4) = 3 logx81 = 4

Answer 1

log_3(2x+15)=2 and log_4(-20x+4)=3

Explanation:

Plug it in and see!

`log_3(2x+15)=2\\log_3(2(-3)+15)=2\\log_3(-6+15)=2\\log_3(9)=2\\\text{ This is a true equation because } 3^2=9\\\\\\log_5(8(-3)+9)=2\\log_5(-24+9)=2\\log_5(-15)=2\\\\\text{ Not true because you cannot do log of a negative number }\\\\log_4(-20(-3)+4)=3\\log_4(64)=3\\\text{ this is true because } 4^3=64\\\\\\log_x (81)=4\\log_(-3)(81)=4\\\text{ the base cannot be negative }\\\\\\\\\text{ There is only two options here} \\\\log_3(2x+15)=2 \text{ and } log_4(-20x+4)=3`

Answer 2

A and C

Explanation: