Find a basis for the space of polynomials p(x) having degree at most 3. Find a basis for the subspace of polynomials p(x) having degree at most 3 with p(1)

Respuesta :

Answer:

[tex] p(x) = ax^3 +bx^2 +cx +d [/tex]

Where a,b,c,d represent constants.

For case given we have this:

[tex] p(1)= a + b+c+d [/tex]

And we need that [tex] p(1)=0[/tex]

[tex] p(1)= a + b+c+d=0[/tex]

That's satisfied if [tex] d = -(a+b+c)[/tex]

[tex] p(x) = ax^3 +bx^2 +cx -(a+b+c) [/tex]

Where [tex] a,b,c,d \in R[/tex]

So then a possible basis for this case would be:

[tex] B= [x^3 -1, x^2 -1 , x-1][/tex]

And we can check that the spans for the subspace is linearly independent.

Step-by-step explanation:

We want to find a basis for the subspace of all polynomials with degree [tex] \leq 3[/tex] and we need to satisfy the condition that [tex] p(1) =0[/tex]

Our general expression for an element of the space described above is given by this equation:

[tex] p(x) = ax^3 +bx^2 +cx +d [/tex]

Where a,b,c,d represent constants.

For case given we have this:

[tex] p(1)= a + b+c+d [/tex]

And we need that [tex] p(1)=0[/tex]

[tex] p(1)= a + b+c+d=0[/tex]

That's satisfied if [tex] d = -(a+b+c)[/tex]

So we want a basis for the subsapce of all the polynomials on this form:

[tex] p(x) = ax^3 +bx^2 +cx -(a+b+c) [/tex]

Where [tex] a,b,c,d \in R[/tex]

So then a possible basis for this case would be:

[tex] B= [x^3 -1, x^2 -1 , x-1][/tex]

And we can check that the spans for the subspace is linearly independent.