Use synthetic division to divide the polynomial 3x4+2x2−5x+6

by x−1
.

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1 answer

To use synthetic division to divide the polynomial \( 3x^4 + 0x^3 + 2x^2 - 5x + 6 \) by \( x - 1 \), we first note the root of the divisor \( x - 1 \), which is \( 1 \).

Step 1: Write down the coefficients

Write down the coefficients of the polynomial:

  • Coefficient of \( x^4 \): 3
  • Coefficient of \( x^3 \): 0 (since there is no \( x^3 \) term)
  • Coefficient of \( x^2 \): 2
  • Coefficient of \( x^1 \): -5
  • Constant term: 6

Thus, the coefficients are: \[ 3, 0, 2, -5, 6 \]

Step 2: Set up Synthetic Division

We set up the synthetic division using the root \( 1 \).

1 |  3   0   2   -5   6
   |       

Step 3: Perform the synthetic division

  1. Bring down the first coefficient (3):
1 |  3   0   2   -5   6
   |         
   |  3  
  1. Multiply the value you just wrote down by the divisor root (1):

    • \( 3 \times 1 = 3 \)
  2. Add this value to the next coefficient (0):

    • \( 0 + 3 = 3 \)
1 |  3   0   2   -5   6
   |        3
   |  3   3  
  1. Repeat steps 2 and 3 for the remaining coefficients:
    • Multiply \( 3 \times 1 = 3 \), then add to 2:
      • \( 2 + 3 = 5 \)
    • Multiply \( 5 \times 1 = 5 \), then add to -5:
      • \( -5 + 5 = 0 \)
    • Multiply \( 0 \times 1 = 0 \), then add to 6:
      • \( 6 + 0 = 6 \)
1 |  3   0   2   -5   6
   |        3   5   0
   |  3   3   5   0   6

Step 4: Write down the result

The bottom row contains the coefficients of the quotient polynomial and the remainder.

The quotient polynomial is:

  • Coefficients: \( 3, 3, 5, 0 \) corresponds to \( 3x^3 + 3x^2 + 5x + 0\)

The remainder is \( 6 \).

Final result

Thus, we can express the original division as: \[ 3x^4 + 2x^2 - 5x + 6 = (x - 1)(3x^3 + 3x^2 + 5x) + 6 \]

Quotient: \( 3x^3 + 3x^2 + 5x \)
Remainder: \( 6 \)