DAT Destroyer math question

[hope_to_match]

From 2013 edition, QR section, question # 54:

Q: Which number is the discriminant of a quadratic equation whose roots are real, unequal, and irrational?
a) 0
b) -5
c) 7
d) 4
e) -9

I read the explanation in the back, but I am having trouble understanding what the question is asking. I know what the quadratic equation is and also the definition of a real number and irrational number. What is meant by unequal? What is the question really asking?

Thanks for all of your help in advance.

---

Members don't see this ad.

 

[KyoPhan]

The question seems to be asking which of the answers, when sqrooted will give you a real, unequal, and irrational number.


The negatives, when sqrooted, will give you imaginary numbers, which are not real numbers.
Sqroot of 0 is equal to sqroot of 0.
sqroot of 4 gives you 2. 2 is a real, unequal to 4, but not an irrational number.
7 is unequal to sqroot of 7. Sqroot of 7 is real, and irrational. So this should be the correct answer?

 

[damnshawty]

From 2013 edition, QR section, question # 54:

Q: Which number is the discriminant of a quadratic equation whose roots are real, unequal, and irrational?
a) 0
b) -5
c) 7
d) 4
e) -9

I read the explanation in the back, but I am having trouble understanding what the question is asking. I know what the quadratic equation is and also the definition of a real number and irrational number. What is meant by unequal? What is the question really asking?

Thanks for all of your help in advance.

right off the bat you can eliminate -5 and -9 because they would give you irrational values. Eliminate 0 because it would give you two equal values, eliminate 4 because although you would get real and unequal values, they would NOT be irrational. 7 is the answer :3

 

[Moka11]

Instead of starting a new thread I thought Id just add to this one.

Destroyer Math PT 9 Q 15: Three dices are rolled. What is the probability of getting two sixes and a one in any order?
In any order means order doesn't matter correct? If order doesn't matter than shouldn't it be the product of each roll independent of the other? i.e. 1/6*1/6*1/6?


(I don't think I will ever fully understand Permutations, Combinations and statistics)

 

[pakipuertorican]

Permutations and Combinations can be a bit tricky. If you have subscription to Chad's, I recommend his QR video over this topic. It really gets down to the point and his quiz really helped me.

If order doesn't matter, you can roll (1,6,6) (6,6,1) or (6,1,6) = 3 different combinations that work
Probabilities are what works / total possible combinations. If you have 3 dice, there are 6 different numbers on each so 6*6*6 gives you a total of 216 combinations.

3/216 = 1/72 which should give you your answer. Hope this helped!

 

[drsuess]

Permutations and Combinations can be a bit tricky. If you have subscription to Chad's, I recommend his QR video over this topic. It really gets down to the point and his quiz really helped me.

If order doesn't matter, you can roll (1,6,6) (6,6,1) or (6,1,6) = 3 different combinations that work
Probabilities are what works / total possible combinations. If you have 3 dice, there are 6 different numbers on each so 6*6*6 gives you a total of 216 combinations.

3/216 = 1/72 which should give you your answer. Hope this helped!

I'm confused with this question. There are obviously 3 combinations that work, but doesn't each combination have 2 possibilities. Why can't the sixes invert?

Let's call the dice A, B, and C. For instance, in the first combination (1,6,6) couldn't you have (A, B, C) and (A, C, B). Since order doesn't matter shouldn't each of the combinations have 2 possibilities to account for the sixes being from either die?