3a-6b/3ab Steps please. Not sure if I originally did this question correctly.
1 answer:
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Answer:
f(r) = (x -1)(x -4+√7)(x -4-√7)
Step-by-step explanation:
The signs of the terms are + - + -. There are 3 changes in sign, so Descartes' rule of signs tells you there are 3 or 1 positive real roots.
The rational roots, if any, will be factors of 9, the constant term. The sum of coefficients is 1 -9 +17 -9 = 0, so you know that r=1 is one solution to f(r) = 0. That means (r -1) is a factor of the function.
Using polynomial long division, synthetic division (2nd attachment), or other means, you can find the remaining quadratic factor to be r^2 -8r +9. The roots of this can be found by various means, including completing the square:
r^2 -8r +9 = (r^2 -8r +16) +9 -16 = (r -4)^2 -7
This is zero when ...
(r -4)^2 = 7
r -4 = ±√7
r = 4±√7
Now, we know the zeros are {1, 4+√7, 4-√7), so we can write the linear factorization as ...
f(r) = (r -1)(r -4 -√7)(r -4 +√7)
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<em>Comment on the graph</em>
I like to find the roots of higher-degree polynomials using a graphing calculator. The red curve is the cubic. Its only rational root is r=1. By dividing the function by the known factor, we have a quadratic. The graphing calculator shows its vertex, so we know immediately what the vertex form of the quadratic factor is. The linear factors are easily found from that, as we show above. (This is the "other means" we used to find the quadratic roots.)
Answer:
(1) 0.5933
(2) 0.8955
Step-by-step explanation:
We are given that all bags entering a research facility are screened.
Let Probability that bags entering the building contains forbidden material,
P(F) = 0.69
Probability that bags entering the building does not contains forbidden material, P(NF) = 1 - 0.69 = 0.31
Let event A = alarm gets triggered
Probability that alarm gets trigger given the bags contain forbidden material, P(A/F) = 0.77
Probability that alarm gets trigger given the bags does not contain forbidden material, P(A/NF) = 0.20
(1) Probability that a bag triggers the alarm, P(A) ;
P(A) = P(F) * P(A/F) + P(NF) * P(A/NF)
= (0.69 * 0.77) + (0.31 * 0.20) = 0.5313 + 0.062
= 0.5933
Therefore, probability that a bag triggers the alarm is 0.5933 .
(2) Probability that a bag that triggers the alarm will actually contain forbidden material is given by P(F/A) ;
Using Bayes' Theorem;
P(F/A) = =
=
= 0.8955