Mr. asked in Science & MathematicsMathematics · 9 years ago

# How do i solve this logarithmic expression??-10 points!?

Given that log(3)4 =p and log (3)5 =q , find the value of x if log(3)x= 2p-q+2

Ive gotten this far. 2log(3)4 - log(3)5 +2 ===> log(3)16 - log(3)5 +2 ====> log(3)16/log(3)5 +2===> 16/5 +2 , now what is the value of x? And is there an error? The answer is 144/5. Please explain

Plus

If log(5)p - log(5)4 =2 find the value of p, do i solve like this? P/4 = 2 then p=8 ... But the answer sheet says im wrong. Please explain my errors...

Lastly, if log(2)x^3 +log(2)x=8, find the value of x====> x^3 +x-8=0 .... How do i solve thhis? Please explain with step by step method

Relevance
• iceman
Lv 7
9 years ago

log3(x) = 2p - q + 2

log3(x) = 2log3(4) - log3(5) + 2

log3(x) = log3[16/5] + 2

x = 3^ {log3[16/5] + 2}

x = 16/5 * 3^2

x = 144/5

log5(p) - log5(4) =2

log5(p/4) = 2

p/4 = 5^2 = 25

p = 4*25 = 100

log2(x^3) +log2(x) = 8

log2(x^3 * x) = 8

log2(x^4) = 8

x^4 = 2^8 = 256

x^4 = 4^4

x = 4

Regards.

• 9 years ago

Given that log(3)4 =p and log (3)5 =q ,

find the value of x if log(3)x= 2p-q+2

log(3)x = 2p-q+2 = 2[log(3)4] -log(3)5 +2 =

= log(3)[4^2/5] +2 = log(3)3.2 + 2 =

= log(3.2) / log3 +2 = 0.50515/0.477122 +2 =

log(3)x = 1.05875 +2 = 3.05875

logx/log3 = 3.05875,

logx = 3.05875(log3) = log(3^3.05875)

SO,

x = 3^3.05875 = 28.8 = 144/5 >=================< ANSWER

2.

log(5)p - log(5)4 = 2 = log(5)25

log(5)[p/4] = log(5)25

p/4 = 25.

SO,

p = 4*25 = 100 >==========================< ANSWER

3.

log(2)x^3 +log(2)x = 8 = log(2)256

log(2)[x^3*x] = log(2)256

x^4 = 256 = 4^4

So,