Question #3624b

2 Answers
Jun 13, 2017

x=log_(25/32)500

Explanation:

5^(2x-3)-2^(5x+2)=0
5^(2x-3)=2^(5x+2)
Taking the natural logarithm of both sides,
ln(5^(2x-3))=ln(2^(5x+2))
(2x-3)ln5=(5x+2)ln2
(2ln5)x-3ln5=(5ln2)x+2ln2
(2ln5)x-(5ln2)x=3ln5+2ln2
[ln(5^2)-ln(2^5)]x=ln(5^3)+ln(2^2)
x=ln(5^3*2^2)/ln(5^2/2^5)
x=ln(125*4)/ln(25/32)
x=log_(25/32)500

Jun 13, 2017

Given: 5^(2x-3)-2^(5x+2)= 0

Move the second term to the right:

5^(2x-3)=2^(5x+2)

Use the base 5 logarithm on both sides:

log_5(5^(2x-3))=log_5(2^(5x+2))

Use the identity log_b(a^c) = (c)log_b(a) on both sides:

(2x-3)log_5(5)=(5x+2)log_5(2)

Use the property log_b(b) = 1 on the left:

2x-3=(5x+2)log_5(2)

Use the distributive property on the right:

2x-3=5log_5(2)x+2log_5(2)

Subtract 5log_5(2)x from both sides:

(2-5log_5(2))x-3=2log_5(2)

Add 3 to both sides:

(2-5log_5(2))x=3+2log_5(2)

Divide both sides by the coefficient of x:

x=(3+2log_5(2))/(2-5log_5(2))

Convert to base e by using the conversion formula log_5(x)= ln(x)/ln(5):

x=(3+2ln(2)/ln(5))/(2-5ln(2)/ln(5))

Multiply by 1 in the form of ln(5)/ln(5):

x=(3ln(5)+2ln(2))/(2ln(5)-5ln(2))