The expression (-4x + 9)^2 cannot be equal to (-4x)^2 + 9^2 because it is actually equal to the product of two factors (3 + 2sqrt x) (3- 2 sqrt x). One cannot use obviously distributive property. Hence the answer to this problem should be C. as she did not understand both perfect square trinomial and did not determine the product
We are choosing 2
2
r
shoes. How many ways are there to avoid a pair? The pairs represented in our sample can be chosen in (2)
(
n
2
r
)
ways. From each chosen pair, we can choose the left shoe or the right shoe. There are 22
2
2
r
ways to do this. So of the (22)
(
2
n
2
r
)
equally likely ways to choose 2
2
r
shoes, (2)22
(
n
2
r
)
2
2
r
are "favourable."
Another way: A perhaps more natural way to attack the problem is to imagine choosing the shoes one at a time. The probability that the second shoe chosen does not match the first is 2−22−1
2
n
−
2
2
n
−
1
. Given that this has happened, the probability the next shoe does not match either of the first two is 2−42−2
2
n
−
4
2
n
−
2
. Given that there is no match so far, the probability the next shoe does not match any of the first three is 2−62−3
2
n
−
6
2
n
−
3
. Continue. We get a product, which looks a little nicer if we start it with the term 22
2
n
2
n
. So an answer is
22⋅2−22−1⋅2−42−2⋅2−62−3⋯2−4+22−2+1.
2
n
2
n
⋅
2
n
−
2
2
n
−
1
⋅
2
n
−
4
2
n
−
2
⋅
2
n
−
6
2
n
−
3
⋯
2
n
−
4
r
+
2
2
n
−
2
r
+
1
.
This can be expressed more compactly in various ways.
We have the expression
We can already simplify x because it's both on the numerator and denominator
Now we can simplify 425/25 = 17
Remember that
Then
The final result is
The first step for solving this inequality is to move the constant to the right side by adding its opposites to both sides. This will look like the following:
y - 6 + 6 ≥ 12 + 6
Eliminate the opposites on the left side.
y ≥ 12 + 6
Lastly,, add the numbers on the right side together to get your final answer.
y ≥ 18
Let me know if you have any further questions.
:)
Answer:
136 minutes
Step-by-step explanation:
Given :
2 miles ----> takes 17 min
1 mile -----> takes 17/2 min
hence the unit rate is (17/2) min per mile
Thus, 16 miles will take
= (17/2) miles per min x 16 miles
= (17/2) x 16
= 136 minutes
