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# Help on polynomials?

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How do you do these problems?

Let $f(x) = x^4-3x^2 + 2$ and $g(x) = 2x^4 - 6x^2 + 2x -1$. Let $a$ be a constant. What is the largest possible degree of $f(x) + a\cdot g(x)$?

Let $f(x) = x^4-3x^2 + 2$ and $g(x) = 2x^4 - 6x^2 + 2x -1$. Let $b$ be a constant. What is the smallest possible degree of the polynomial $f(x) + b\cdot g(x)$?

and

There is a polynomial which, when multiplied by $x^2 + 2x + 3$, gives $2x^5 + 3x^4 + 8x^3 + 8x^2 + 18x + 9$. What is that polynomial? (Give your answer as a polynomial in which the terms appear in order of decreasing degree. In other words, "$x^5 + x + 2$" is a valid answer, but "$2+x^5+x$" is not.)

Thanks

Aug 3, 2018
edited by Guest  Aug 3, 2018
edited by Guest  Aug 3, 2018

### 1+0 Answers

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The degree of a polynomial is determined by the largest power of x that occurs.  Multiplying by a constant, no matter how big, makes no difference.

So, in "Let f(x) = x^4-3x^2 + 2 and g(x) = 2x^4 - 6x^2 + 2x -1. Let a be a constant. What is the largest possible degree of f(x) + a.g(x)?", the degree is 4.

Now, with that knowledge, see if you can do the other parts of your question.

Aug 4, 2018