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how do you go from x-16x^1/2+15=0 to x^2+225=226x

Here is the mark scheme

http://qualifications.pearson.com/content/dam/pdf/A%20Level/Mathematics/2013/Exam%20materials/Mark-scheme-Unit-C2-(6664)-Paper-1R-June-2014.pdf

question 8ii) and how they factorise it. I don't understand this question though as there is no power of 2

(edited 3 years ago)

Square both sides

Original post by Blueberry.89

Square both sides

well my method would to tidy this up since X^y*X^Y=X^2y I can get rid of that half by replacing X^1/2 with y so now we have

Y^2-16y+15=0 etc etc but then thats to get the value of X if I want to get from one side to the other like this then yes
X+15=16x^1/2 squaring gives
X^2+225=256X

so maybe a mistake somewhere but no and here is why

(X+15)(X+15)=x^2 +15x+15x+225
=X^2+30x+225
now (16^1/2)=256

so
X^2+30x+225=256x
now
x^2+225=256x-30x
x^2+225=226x

this may be a different way to explaining then how you explained it but this shows common mistakes people make and may be where he got confused.

i deliberately make mistake at first to show how you can go wrong then show how it works broken down