Show that S x2 3x 1 2x2 x 1 4x is or is not a basis for
Show that S = {x^2 + 3x + 1, 2x^2 + x - 1, 4x} is or is not a basis for P_2?
Solution
a( x^2 +3x -1) +b(2x^2 +x -1) +c(4x) =0
x^2(a +b) + x( 3a +b +4c) -a -b =0
a+b =0
3a +b +4c =0
-a -b =0
a = -b
So, 3a -a +4c =0 ; c= a
So,b = -a , c = a ;
So, a = b = c =0
Hence vectors are linearly indpenedent and S is a basis for P2
