completing the square refreshing

[maths_arghh234]

a) express 2x(squared) +4x+5 in the form a(x+b)squared +c where a, b and c are to be determined

b) use the result derived in a to find the greatest value of 1/2x(squared) +4x +5

i've tried a but i think i#m doing it wrong what i've done is a=2 b=4 c=5 so 2(x+4)squared +5 but it doesn't seem enough so i'm pretty sure i'm forgeting something :\ ... but i just can't of what it is please help !! thanks

 

[tutor_joel]

What you need to do is put this in vertex form by completing the square. Here is a good primmer on how to do that. Once you have the equation in vertex form, finding the max value is easy.