Show that $B$ is a basis of $mathbb{P}_{2}$












0












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Im asked to prove that $B$ is a basis of $mathbb{P}_{2}$. I know how to show that $B$ is a basis of $mathbb{R}^{3}$ but i don't know how to do it with polynomials. This is the exercise:



Show that $B = {1+x,2+x-x^2,1}$ is a basis of the vector space $mathbb{P}_{2} = $Span${1,x,x^2}$










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  • 3




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    It is equivalent to showing that $[1,1,0], [2,1,-1], [1,0,0]$ is a basis of $mathbb R^3$.
    $endgroup$
    – Robert Israel
    Jan 22 at 16:45










  • $begingroup$
    What do you mean $B$ is a basis of $mathbb{R}^{3}$? $B$ is not even a subset of $mathbb{R}^{3}$
    $endgroup$
    – pwerth
    Jan 22 at 16:54
















0












$begingroup$


Im asked to prove that $B$ is a basis of $mathbb{P}_{2}$. I know how to show that $B$ is a basis of $mathbb{R}^{3}$ but i don't know how to do it with polynomials. This is the exercise:



Show that $B = {1+x,2+x-x^2,1}$ is a basis of the vector space $mathbb{P}_{2} = $Span${1,x,x^2}$










share|cite|improve this question











$endgroup$








  • 3




    $begingroup$
    It is equivalent to showing that $[1,1,0], [2,1,-1], [1,0,0]$ is a basis of $mathbb R^3$.
    $endgroup$
    – Robert Israel
    Jan 22 at 16:45










  • $begingroup$
    What do you mean $B$ is a basis of $mathbb{R}^{3}$? $B$ is not even a subset of $mathbb{R}^{3}$
    $endgroup$
    – pwerth
    Jan 22 at 16:54














0












0








0





$begingroup$


Im asked to prove that $B$ is a basis of $mathbb{P}_{2}$. I know how to show that $B$ is a basis of $mathbb{R}^{3}$ but i don't know how to do it with polynomials. This is the exercise:



Show that $B = {1+x,2+x-x^2,1}$ is a basis of the vector space $mathbb{P}_{2} = $Span${1,x,x^2}$










share|cite|improve this question











$endgroup$




Im asked to prove that $B$ is a basis of $mathbb{P}_{2}$. I know how to show that $B$ is a basis of $mathbb{R}^{3}$ but i don't know how to do it with polynomials. This is the exercise:



Show that $B = {1+x,2+x-x^2,1}$ is a basis of the vector space $mathbb{P}_{2} = $Span${1,x,x^2}$







linear-algebra






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edited Jan 22 at 16:53









pwerth

3,265417




3,265417










asked Jan 22 at 16:43









Juan HernándezJuan Hernández

32




32








  • 3




    $begingroup$
    It is equivalent to showing that $[1,1,0], [2,1,-1], [1,0,0]$ is a basis of $mathbb R^3$.
    $endgroup$
    – Robert Israel
    Jan 22 at 16:45










  • $begingroup$
    What do you mean $B$ is a basis of $mathbb{R}^{3}$? $B$ is not even a subset of $mathbb{R}^{3}$
    $endgroup$
    – pwerth
    Jan 22 at 16:54














  • 3




    $begingroup$
    It is equivalent to showing that $[1,1,0], [2,1,-1], [1,0,0]$ is a basis of $mathbb R^3$.
    $endgroup$
    – Robert Israel
    Jan 22 at 16:45










  • $begingroup$
    What do you mean $B$ is a basis of $mathbb{R}^{3}$? $B$ is not even a subset of $mathbb{R}^{3}$
    $endgroup$
    – pwerth
    Jan 22 at 16:54








3




3




$begingroup$
It is equivalent to showing that $[1,1,0], [2,1,-1], [1,0,0]$ is a basis of $mathbb R^3$.
$endgroup$
– Robert Israel
Jan 22 at 16:45




$begingroup$
It is equivalent to showing that $[1,1,0], [2,1,-1], [1,0,0]$ is a basis of $mathbb R^3$.
$endgroup$
– Robert Israel
Jan 22 at 16:45












$begingroup$
What do you mean $B$ is a basis of $mathbb{R}^{3}$? $B$ is not even a subset of $mathbb{R}^{3}$
$endgroup$
– pwerth
Jan 22 at 16:54




$begingroup$
What do you mean $B$ is a basis of $mathbb{R}^{3}$? $B$ is not even a subset of $mathbb{R}^{3}$
$endgroup$
– pwerth
Jan 22 at 16:54










1 Answer
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$begingroup$

Let $a,b,c in mathbb R$ and $a(1+x)+b(2+x-x^2)+c=0$ for all x$ in mathbb R$.



If you can show that $a=b=c=0$, then you are done.






share|cite|improve this answer









$endgroup$













  • $begingroup$
    Technically, one also has to show that the the polynomials span $Bbb P^2$.
    $endgroup$
    – Arthur
    Jan 22 at 17:04











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1 Answer
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active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









1












$begingroup$

Let $a,b,c in mathbb R$ and $a(1+x)+b(2+x-x^2)+c=0$ for all x$ in mathbb R$.



If you can show that $a=b=c=0$, then you are done.






share|cite|improve this answer









$endgroup$













  • $begingroup$
    Technically, one also has to show that the the polynomials span $Bbb P^2$.
    $endgroup$
    – Arthur
    Jan 22 at 17:04
















1












$begingroup$

Let $a,b,c in mathbb R$ and $a(1+x)+b(2+x-x^2)+c=0$ for all x$ in mathbb R$.



If you can show that $a=b=c=0$, then you are done.






share|cite|improve this answer









$endgroup$













  • $begingroup$
    Technically, one also has to show that the the polynomials span $Bbb P^2$.
    $endgroup$
    – Arthur
    Jan 22 at 17:04














1












1








1





$begingroup$

Let $a,b,c in mathbb R$ and $a(1+x)+b(2+x-x^2)+c=0$ for all x$ in mathbb R$.



If you can show that $a=b=c=0$, then you are done.






share|cite|improve this answer









$endgroup$



Let $a,b,c in mathbb R$ and $a(1+x)+b(2+x-x^2)+c=0$ for all x$ in mathbb R$.



If you can show that $a=b=c=0$, then you are done.







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Jan 22 at 16:54









FredFred

48k1849




48k1849












  • $begingroup$
    Technically, one also has to show that the the polynomials span $Bbb P^2$.
    $endgroup$
    – Arthur
    Jan 22 at 17:04


















  • $begingroup$
    Technically, one also has to show that the the polynomials span $Bbb P^2$.
    $endgroup$
    – Arthur
    Jan 22 at 17:04
















$begingroup$
Technically, one also has to show that the the polynomials span $Bbb P^2$.
$endgroup$
– Arthur
Jan 22 at 17:04




$begingroup$
Technically, one also has to show that the the polynomials span $Bbb P^2$.
$endgroup$
– Arthur
Jan 22 at 17:04


















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