(4x^4+5x-4)/(x^2-3x-2) Long Division

6 min read Jun 16, 2024
(4x^4+5x-4)/(x^2-3x-2) Long Division

Long Division of Polynomials: (4x^4 + 5x - 4) / (x^2 - 3x - 2)

Long division of polynomials is a method used to divide a polynomial by another polynomial of a lower or equal degree. This process is similar to the long division of numbers. Let's dive into how to perform this division with the example: (4x^4 + 5x - 4) / (x^2 - 3x - 2).

Step 1: Set up the division.

Write the problem in the standard long division format, with the dividend (4x^4 + 5x - 4) inside the division symbol and the divisor (x^2 - 3x - 2) outside.

            ___________
x^2 - 3x - 2 | 4x^4 + 0x^3 + 0x^2 + 5x - 4 

Note: We add 0x^3 and 0x^2 as placeholders to ensure that each term in the dividend is accounted for.

Step 2: Divide the leading terms.

Divide the leading term of the dividend (4x^4) by the leading term of the divisor (x^2). This gives us 4x^2.

            4x^2       
x^2 - 3x - 2 | 4x^4 + 0x^3 + 0x^2 + 5x - 4 

Step 3: Multiply the quotient by the divisor.

Multiply the quotient (4x^2) by the divisor (x^2 - 3x - 2). This gives us 4x^4 - 12x^3 - 8x^2.

            4x^2       
x^2 - 3x - 2 | 4x^4 + 0x^3 + 0x^2 + 5x - 4 
             4x^4 - 12x^3 - 8x^2

Step 4: Subtract the result from the dividend.

Subtract the result (4x^4 - 12x^3 - 8x^2) from the dividend (4x^4 + 0x^3 + 0x^2 + 5x - 4). This leaves us with 12x^3 + 8x^2 + 5x - 4.

            4x^2       
x^2 - 3x - 2 | 4x^4 + 0x^3 + 0x^2 + 5x - 4 
             4x^4 - 12x^3 - 8x^2
             ---------------------
                    12x^3 + 8x^2 + 5x - 4

Step 5: Repeat steps 2-4.

Bring down the next term of the dividend (5x). Now, divide the leading term of the new dividend (12x^3) by the leading term of the divisor (x^2). This gives us 12x.

            4x^2 + 12x    
x^2 - 3x - 2 | 4x^4 + 0x^3 + 0x^2 + 5x - 4 
             4x^4 - 12x^3 - 8x^2
             ---------------------
                    12x^3 + 8x^2 + 5x - 4
                    12x^3 - 36x^2 - 24x

Subtract the result (12x^3 - 36x^2 - 24x) from the previous result (12x^3 + 8x^2 + 5x - 4). This leaves us with 44x^2 + 29x - 4.

            4x^2 + 12x    
x^2 - 3x - 2 | 4x^4 + 0x^3 + 0x^2 + 5x - 4 
             4x^4 - 12x^3 - 8x^2
             ---------------------
                    12x^3 + 8x^2 + 5x - 4
                    12x^3 - 36x^2 - 24x
                    ---------------------
                            44x^2 + 29x - 4

Step 6: Repeat steps 2-4 again.

Bring down the next term of the dividend (-4). Now, divide the leading term of the new dividend (44x^2) by the leading term of the divisor (x^2). This gives us 44.

            4x^2 + 12x + 44    
x^2 - 3x - 2 | 4x^4 + 0x^3 + 0x^2 + 5x - 4 
             4x^4 - 12x^3 - 8x^2
             ---------------------
                    12x^3 + 8x^2 + 5x - 4
                    12x^3 - 36x^2 - 24x
                    ---------------------
                            44x^2 + 29x - 4
                            44x^2 - 132x - 88

Subtract the result (44x^2 - 132x - 88) from the previous result (44x^2 + 29x - 4). This leaves us with 161x + 84.

            4x^2 + 12x + 44    
x^2 - 3x - 2 | 4x^4 + 0x^3 + 0x^2 + 5x - 4 
             4x^4 - 12x^3 - 8x^2
             ---------------------
                    12x^3 + 8x^2 + 5x - 4
                    12x^3 - 36x^2 - 24x
                    ---------------------
                            44x^2 + 29x - 4
                            44x^2 - 132x - 88
                            ---------------------
                                   161x + 84

Step 7: The remainder.

Since the degree of the remainder (161x + 84) is less than the degree of the divisor (x^2 - 3x - 2), we stop here.

Result:

Therefore, the result of the long division is:

(4x^4 + 5x - 4) / (x^2 - 3x - 2) = 4x^2 + 12x + 44 + (161x + 84) / (x^2 - 3x - 2)

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