# Math Help - Easy Surd, frustrated...

1. ## Easy Surd, frustrated...

Give in form a+b√2

(3-√8)²

9-3√8-3√8+4

13-6
√8

13-12
√2

book says i'm wrong can't understand why

2. Originally Posted by alibond07
Give in form a+b√2

(3-√8)²

9-3√8-3√8+4 e^(i*pi): Where did +4 come from? $(-\sqrt8)^2 = 8$

13-6
√8

13-12
√2

book says i'm wrong can't understand why

$(3-\sqrt8)^2 = 9-6\sqrt8+8 = 17-6\sqrt8 = 17-12\sqrt2$

3. Thanks got it now, just made a careless mistake with the -√8x-√8.