Exponents and Logarithms
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SAT Subject Test in Math I › Exponents and Logarithms
Simplify:
Explanation
When adding exponents, we don't add the exponents or multiply out the bases. Our goal is to see if we can factor anything. We do see three . Let's factor.
Remember when multiplying exponents, we just add the powers.
Give the set of real solutions to the equation
(round to the nearest hundredth, if applicable)
Explanation
Using the Product of Powers Rule, then the Power of a Power Rule, rewrite the first term:
Substitute for
; the equation becomes
,
which is quadratic in terms of . The trinomial might be factorable using the
method, where we split the middle term with integers whose product is
and whose sum is 11. By trial and error, we find the integers to be 12 and
, so the equation can be written as follows:
Factoring by grouping:
By the Zero Product Rule, one of these two factors must be equal to 0.
If , then
.
Substituting back for
, we get
.
This is impossible, since any power of a positive number must be positive.
If , then:
Substituting back for
, we get
Since ,
it holds that , and
, the only solution.
Explanation
By the Power of a Power and Product of Power Rules, we can rewrite this equation as
Substitute for
; the resulting equation is the quadratic equation
,
which can be written in standard form by subtracting from both sides:
The quadratic trinomial fits the perfect square trinomial pattern:
By the square root principle,
Substituting for
:
Simplify:
Explanation
When dealing with subtraction in regards to logarithms, it's the same as dividing the numbers.
Solve for :
No solution
Explanation
, so the equation
can be rewritten as:
By the Power of a Power rule:
It follows that
Solving for :
How many elements are in a set that has exactly 128 subsets?
None of the other responses is correct.
Explanation
A set with elements has
subsets.
Solve:
Simplify:
Explanation
When dealing with addition in regards to logarithms, it's the same as multiplying the numbers.
Simplify:
Explanation
is the same as
. Let's factor out
. It's the same as
. Therefore
which is the answer to our question.
Rewrite as a single logarithmic expression:
Explanation
Using the properties of logarithms
and
,
we simplify as follows:
Solve for (round to the nearest hundredth):
Explanation
Take the natural logarithm of both sides:
By Logarithm of a Power Rule, the above becomes
After distributing, solve for :
Factor out the left side, then divide:
Substituting the values of the logarithms:
This rounds to 0.45.