Answer:
Assume ΔABC is an acute triangle.
Step-by-step explanation:
Given the triangle ABC.
We have to tell the first step of indirect proving ΔABC is not an acute triangle.
An indirect proof, also known a proof by contradiction. When we use indirect proof method, we assume the opposite of our theory to be true and then by applying our assumed theory we contradict the given statement which proves our supposition is wrong. In other words, we assume our theory is false.
Hence, our first step is to
Assume ΔABC is an acute triangle.
Third option is correct.
Answer:
Step-by-step explanation:
To solve this problem you must apply the proccedure shown below:
1. You need to apply the Distributive property on the left member of the equation:
2. Now, you must solve for 
, as following:
Let BS be the event that the patient survives bypass surgery.
Let H be the event that the heart damage will heal.
Then P(BS) = 0.60, and also we have a conditional probability: GIVEN that the patient survives,
the probability that the heart damage will heal is 0.5, that is P(H|BS) = 0.5
We want to know P(BS and H).
Using the formula of the conditional probability:
P(H and BS) = P(H|BS)·P(BS) = (0.6)(0.5) = 0.3
When applying indirect proofs, we assume the negation of the conclusion is true, and show that this assumption would lead to nonsense, or contradiction.
In our case we assume a is not smaller than 7, that is we assume a≥7.
a≥7 then, multiplying both sides by 3:
3a≥21, then, adding both sides 7:
3a+7≥28,
which is a contradiction because 3a+7 is smaller than 28.
So our assumption is wrong, which means the opposite of it is correct.
Answer: assume a≥7
