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If [tex]f(x) = 3x^5 - 4x^3 + ax + x - 7[/tex] and [tex]g(x) = -3x^5 + 4x^3 + 6x^2 - x + 7[/tex], find [tex]f(x) + g(x)[/tex] and its degree.

Sagot :

To find [tex]\( f(x) + g(x) \)[/tex] and its degree, we need to add the corresponding coefficients of the polynomials [tex]\( f(x) \)[/tex] and [tex]\( g(x) \)[/tex]. Let's break down each polynomial term by term.

Given:
[tex]\[ f(x) = 3x^5 - 4x^3 + ax + x - 7 \][/tex]
[tex]\[ g(x) = -3x^5 + 4x^3 + 6x^2 - x + 7 \][/tex]

First, we align the terms with the same powers:

[tex]\[ \begin{aligned} f(x) &= 3x^5 + 0x^4 - 4x^3 + 0x^2 + (a+1)x - 7, \\ g(x) &= -3x^5 + 0x^4 + 4x^3 + 6x^2 - x + 7. \end{aligned} \][/tex]

Next, we add the corresponding coefficients:

1. Coefficient of [tex]\( x^5 \)[/tex]:
[tex]\[ 3 + (-3) = 0 \][/tex]

2. Coefficient of [tex]\( x^4 \)[/tex]:
[tex]\[ 0 + 0 = 0 \][/tex]

3. Coefficient of [tex]\( x^3 \)[/tex]:
[tex]\[ -4 + 4 = 0 \][/tex]

4. Coefficient of [tex]\( x^2 \)[/tex]:
[tex]\[ 0 + 6 = 6 \][/tex]

5. Coefficient of [tex]\( x \)[/tex]:
[tex]\[ (a + 1) - 1 = a \][/tex]

6. Constant term:
[tex]\[ -7 + 7 = 0 \][/tex]

Therefore, the resulting polynomial [tex]\( f(x) + g(x) \)[/tex] is:

[tex]\[ f(x) + g(x) = 6x^2 + ax \][/tex]

This polynomial can be rewritten as [tex]\( 0x^5 + 0x^4 + 0x^3 + 6x^2 + ax + 0 \)[/tex], making it clear that the highest non-zero coefficient corresponds to the [tex]\( x^2 \)[/tex] term.

The degree of the polynomial [tex]\( f(x) + g(x) \)[/tex] is determined by the highest power of [tex]\( x \)[/tex] with a non-zero coefficient. Thus, the degree of [tex]\( f(x) + g(x) \)[/tex] is:
[tex]\[ \boxed{2} \][/tex]