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3 years ago

What are the solutions of the quadratic equation 4x2 - 8x – 12 = 0?

Mathematics

1 answer:

Juliette [100K]3 years ago

5 0

Answer:

see bottom

Step-by-step explanation:

divide through by 4

x2 - 2x - 3 = 0

x2 - 3x + x - 3 = 0

(x2 - 3x) + (x - 3) = 0

x(x - 3) + 1(x - 3) = 0

(x + 1) (x - 3) = 0

x + 1 = 0 and x - 3 = 0

x = -1 and x = 3

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Arlecino [84]

Answer: $\dfrac{12}{13}$

Step-by-step explanation:

Let A = he known the answer then A' = he guess the answer.

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As per given , we have

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By Bayes theorem , we have

$P(A|B)=\dfrac{P(B|A)P(A)}{P(B|A)P(A)+P(B|A')P(A')}\\\\ P(A|B)=\dfrac{1\times\dfrac{3}{4}}{1\times\dfrac{3}{4}+\dfrac{1}{4}\times\dfrac{1}{4}}\\\\= \dfrac{12}{13}$

The probability that the student knows the answer given that he answered it correctly is $\dfrac{12}{13}$ .

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