Synthetic Division
How to divide a polynomial by a binomial by doing the synthetic division: 2 examples and their solutions.
Example(x3 - 7x + 11)/(x - 2)
The synthetic division is a way
to divide a polynomial by a binomial,
just like the long division.
The numerator is
x3 + 0x2 - 7x + 11.
(If there's a missing term, like the x2 term,
think its coefficient as 0.)
Then write the coefficients of the numerator terms
in descending order:
1 0 -7 11.
Draw an L shape form like this.
On the left side,
write the zero of the denominator (x - 2), 2.
Then, do the synthetic division.
Write 1
in ↓ direction.
↓: 1 = 1
Multiply 1 and the left 2.
Write 1⋅2 = 2
in ↗ direction.
↗: 1⋅2 = 2
Add 0 and 2
in ↓ direction.
↓: 0 + 2 = 2
Multiply 2 and the left 2.
Write 2⋅2 = 4
in ↗ direction.
↗: 2⋅2 = 4
Add -7 and 4
in ↓ direction.
↓: -7 + 4 = -3
Multiply -3 and the left 2.
Write -3⋅2 = -6
in ↗ direction.
↗: -3⋅2 = -6
Add 11 and -6
in ↓ direction.
↓: 11 - 6 = 5
Draw another L shape form
that covers the right end number 5.
This 5 is the remainder.
This is the end of the calculation.
Let's write the answer from this.
The numbers below the L shape,
1 2 3,
are the coefficients of the quotient terms.
So the quotient is
x2 + 2x + 3.
The number in this L shape, 5,
is the remainder.
So write +, a fraction bar,
and 5 in the numerator.
The zero of the left 2 is
(x - 2).
So write (x - 2)
in the denominator.
From the synthetic division,
you can find that
(given) = x2 + 2x + 3 + 5/(x - 2).
So
x2 + 2x + 3 + 5/(x - 2)
is the answer.
Example(2x4 + x3 - 5x2 + 3x + 4) ÷ (x + 1)
The numerator is
2x4 + x3 - 5x2 + 3x + 4.
Then write the coefficients of the numerator terms
in descending order:
2 1 -5 3 4.
Draw an L shape form like this.
On the left side,
write the zero of (x + 1), -1.
Then, do the synthetic division.
Write 2
in ↓ direction.
↓: 2 = 2
Multiply 2 and the left -1.
Write 2⋅(-1) = -2
in ↗ direction.
↗: 2⋅(-1) = -2
Add 1 and -2
in ↓ direction.
↓: 1 - 2 = -1
Multiply -1 and the left -1.
Write (-1)⋅(-1) = 1
in ↗ direction.
↗: (-1)⋅(-1) = 1
Add -5 and 1
in ↓ direction.
↓: -5 + 1 = -4
Multiply -4 and the left -1.
Write (-4)⋅(-1) = 4
in ↗ direction.
↗: (-4)⋅(-1) = 4
Add 3 and 4
in ↓ direction.
↓: 3 + 4 = 7
Multiply 7 and the left -1.
Write 7⋅(-1) = 4
in ↗ direction.
↗: 7⋅(-1) = -7
Add 4 and -7
in ↓ direction.
↓: 4 - 7 = -3
Draw another L shape form
that covers the right end number -3.
This -3 is the remainder.
This is the end of the calculation.
Let's write the answer from this.
The numbers below the L shape,
2 -1 -4 7,
are the coefficients of the quotient terms.
So the quotient is
2x3 - x2 - 4x + 7.
The number in this L shape, -3,
is the remainder.
So write -, a fraction bar,
and 3 in the numerator.
The zero of the left -1 is
(x + 1).
So write (x + 1)
in the denominator.
From the synthetic division,
you can find that
(given) = 2x3 - x2 - 4x + 7 - 3/(x + 1).
So
2x3 - x2 - 4x + 7 - 3/(x + 1)
is the answer.