Express the following as a logarithm and simplify.

1. log(3x^2 + 11x - 20) - log(3x - 4)
2. 1/6 log3 27 + log3 18 - log3 2
3. log5 cube root of 625
4. 2loga x^3 + 3loga y + 4loga z - 3logz w

User Icon for Steve Steve answered
9 years ago

since 3x^2+11x-20 = (3x-4)(x+5) you have

log(3x-4)+log(x+5)-log(3x-4) = log(x+5)

log3(27) = 3
log(18) = log(9) + log(2)
So, you have

1/6 (3) + 2 + log3(2) - log3(2) = 5/2

625 = 5^4, so you have
log5(5^(4/3)) = 4/3

surely you meant loga w. If so, you have

log_a(x^6 y^3 z^4 w^3)

User Icon for Explain Bot Explain Bot answered
11 months ago

To express and simplify logarithmic expressions, we can apply certain rules and properties of logarithms. Let's go through each expression.

1. log(3x^2 + 11x - 20) - log(3x - 4):

To simplify this expression, we can use the quotient property of logarithms, which states that log(a) - log(b) is equivalent to log(a/b).

Thus, we can rewrite the expression as:
log[(3x^2 + 11x - 20)/(3x - 4)]

This is the simplified form of the expression.

2. 1/6 log3 27 + log3 18 - log3 2:

In this expression, we have three terms. We can use the power rule of logarithms, which states that log(base b) a^c is equal to c*log(base b) a.

Let's simplify each term individually:
1/6 log3 27 = 1/6 * 3 = 1/2 (since 3^3 = 27)
log3 18 = log3 (2 * 3^2) = log3 2 + log3 3^2 = log3 2 + 2
log3 2 remains as it is.

Combining these terms, we get:
1/2 + (log3 2 + 2) - log3 2

Since log3 2 and -log3 2 cancel each other out, we are left with:
1/2 + 2 = 2.5

Thus, the simplified form of the expression is 2.5.

3. log5 cube root of 625:

To express this expression as a logarithm, we can use the power rule of logarithms. The cube root of 625 can be written as 5^(2/3), since (5^(2/3))^3 = 625.

Therefore, the expression can be written as:
log5 (5^(2/3))

Since the base of the logarithm (5) and the base of the exponent (5) are the same, the expression simplifies to:
2/3

Thus, the simplified form of the expression is 2/3.

4. 2loga x^3 + 3loga y + 4loga z - 3logz w:

To simplify this expression, we can use the power rule of logarithms. Recall that log(base b) a^c is equal to c*log(base b) a.

Let's simplify each term individually:
2loga x^3 = loga (x^3)^2 = loga x^6
3loga y remains as it is
4loga z remains as it is
-3logz w remains as it is

Combining these terms, we get:
loga x^6 + 3loga y + 4loga z - 3logz w

This is the simplified form of the expression.