B would be correct the -3 x and 3 x cancel out
Answer: 0.9730
Step-by-step explanation:
Let A be the event of the answer being correct and B be the event of the knew the answer.
Given: 


If it is given that the answer is correct , then the probability that he guess the answer 
By Bayes theorem , we have


Hence, the student correctly answers a question, the probability that the student really knew the correct answer is 0.9730.
Answer:
see explanation
Step-by-step explanation:
Given
x +
y +
z = π
let
x = A ,
y = B ,
z = C , so
x = tanA, y = tanB , z = tanC
Substituting values
A + B + C = π ( subtract C from both sides )
A + B = π - C ( take tan of both sides )
tan(A + B) = tan(π - C) = - tanC ( expand left side using addition identity for tan )
= - tanC ( multiply both sides by 1 - tanAtanB )
tanA + tanB = - tanC( 1 - tanAtanB) ← distribute
tanA+ tanB = - tanC + tanAtanBtanC ( add tanC to both sides )
tanA + tanB + tanC = tanAtanBtanC , that is
x + y + z = xyz
(x`-b/2a)-D/4a
(x`-7)+576
answer! (7;-576)