Hey there! Sign in to join this conversationNew here? Join for free
Turn on thread page Beta
    • Thread Starter
    Offline

    2
    ReputationRep:
    Given that 2-4i is a root of the equation
    Z^2+pz+q=0

    Where p+q are real constants,

    (a)Write down the other root of the equation.
    2+4i i believe.

    (b)Find the value of p and the value of q.
    (A=alpha B=beta. Not sure how to get the characters.)
    This is where I get a little bit confused. Would you use the equation x^2-(A-B)x+AB
    But what is A and what is B in this situation?

    Thanks
    • Very Important Poster
    Offline

    21
    ReputationRep:
    Very Important Poster
    (Original post by Connor_leigh)
    Given that 2-4i is a root of the equation
    Z^2+pz+q=0

    Where p+q are real constants,

    (a)Write down the other root of the equation.
    2+4i i believe.

    (b)Find the value of p and the value of q.
    (A=alpha B=beta. Not sure how to get the characters.)
    This is where I get a little bit confused. Would you use the equation x^2-(A-B)x+AB
    But what is A and what is B in this situation?

    Thanks
    Yes, you would.

    Alpha and beta are the roots of the equation.

    You can compare the formula to what you've got.
    • Thread Starter
    Offline

    2
    ReputationRep:
    Surely your Alpha and Beta just cancel though and give you a coefficient of 0x?
    • Study Helper
    Offline

    15
    Study Helper
    (Original post by Connor_leigh)
    (A=alpha B=beta. Not sure how to get the characters.)
    This is where I get a little bit confused. Would you use the equation x^2-(A-B)x+AB
    But what is A and what is B in this situation?

    Thanks
    Not quite.

    If A,B are the two roots, then your quadratic is (x-A)(x-B) giving x^2-(A+B)x+AB

    In "A+B", the imaginary parts cancel, but the real parts don't.
    • Thread Starter
    Offline

    2
    ReputationRep:
    Oh it's (A+B). Thanks, I had the equation wrong.
 
 
 
Poll
“Yanny” or “Laurel”

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.