Help Me Pwease :) (Surds) (1 Viewer)

[Snow Pea!]

umm.. ive always had trouble with the expansion of surds and this one is no different.. its from an unknown sheet that my maths teacher gave me so i dont kno how to work it out or wot the answer is.. anyways the Q is:

if g(x) = xsquared + 5x +3, evaluate g(3root5 -2)

thanks in advance

 

[Cityboy]

answer = 42 + 3root5

wherever there is an x in the g(x) graph you subsitute it with 3root5 - 2

Such that you get the equation (3root5 - 2) squared + 5(3root5 - 2) + 3

 

[insert-username]

g(x) = x² + 5x + 3

Therefore, for g(3√5 -2), you substitute in (3√5 -2) for each x. So...


= (3√5 -2)² + 5(3√5 -2) + 3.

= 45 - 12√5 + 4 + 15√5 - 10 + 3

= 42 + 3√5

= 3(14 + √5)




EDIT: Bah, Cityboy beat me to it.


I_F

 

[Snow Pea!]

thankyou very much both of you!