find the factor of the polynomial x^3-5x^2+8x-4 divide the polynomial with the factor and verify the division rule
Answers
Answer:
Step-by-step explanation:
Use remainder factor theorem
x-1=0
x=1
put the value
x3-8x2+19x-12=0
LHS=
1-8+19-12
=0=RHS
Hence x-1 is a factor of the given expression
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Note:
★ The possible values of the variable for which the polynomial becomes zero are called its zeros .
★ A cubic polynomial can have atmost three zeros .
★ If p(a) = 0 , then x = a is a zero of polynomial p(x) and hence (x - a) is a factor of the polynomial p(x) .
★ If x - a is a factor of the polynomial p(x) then the remainder obtained on dividing p(x) by (x - a) is zero .
Solution:
Here,
The given cubic polynomial is ;
x³ - 5x² + 8x - 4 .
By hit and trial , we get that the polynomial becomes zero at x = 1 .
If x = 1 , then ;
x - 1 = 0 .
Thus,
(x - 1) is a factor of the given cubic polynomial .
Now,
To get another factor let's divide the given polynomial by (x - 1)
x - 1 ) x³ - 5x² + 8x - 4 ( x² - 4x + 4
x³ - x²
– +
- 4x² + 8x
- 4x² + 4x
+ –
4x - 4
4x - 4
– +
× ×
Here,
Dividend = x³ - 5x² + 8x - 4
Divisor = x - 1
Quotient = x² - 4x + 4
Remainder = 0
Also,
We know that ;
Dividend = Divisor×Quotient + Remainder
Now,
=> LHS = Dividend
=> LHS = x³ - 5x² + 8x - 4
Also,
=> RHS = Divisor × Quotient + Remainder
=> RHS = (x² - 4x + 4) × (x - 1)
=> RHS = x³ - x² - 4x² + 4x + 4x - 4
=> RHS = x³ - 5x² + 8x - 4
Clearly,
LHS = RHS
Thus,
Dividend = Divisor×Quotient + Remainder
Hence verified .
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Also ,
We can also verify the division rule using another factor of the given polynomial .
Now,
Dividend = Divisor×Quotient + Remainder
Thus,
=> x³ - 5x² + 8x - 4 = (x²- 4x + 4) × (x - 1) + 0
=> x³ - 5x² + 8x - 4 = (x² - 4x + 4) × (x - 1)
=> x³ - 5x² + 8x - 4 = (x - 2)²(x - 1)
=> x³ - 5x² + 8x - 4 = (x - 1)(x - 2)(x - 2)
Thus,
The given cubic polynomial can be rewritten as
x³ - 5x² + 8x - 4 = (x - 1)(x - 2)(x - 2) .
Hence,
The factors of the given cubic polynomial are ;
(x - 1) , (x - 2) , (x - 2)
Thus,
Let's use another factor (x - 2) to verify the division rule .
Thus,
Let's divide the given polynomial by (x-2) .
x - 2 ) x³ - 5x² + 8x - 4 ( x² - 3x + 2
x³ - 2x²
– +
- 3x² + 8x
- 3x² + 6x
+ -
2x - 4
2x - 4
– +
× ×
Here ,
Dividend = x³ - 5x² + 8x - 4
Divisor = x - 2
Quotient = x² - 3x + 2
Remainder = 0
Also,
We know that ;
Dividend = Divisor×Quotient + Remainder
Now,
=> LHS = Dividend
=> LHS = x³ - 5x² + 8x - 4
Also,
=> RHS = Divisor × Quotient + Remainder
=> RHS = (x² - 3x + 2) × (x - 2) + 0
=> RHS = x³ - 2x² - 3x² + 6x + 2x - 4
=> RHS = x³ - 5x² + 8x - 4
Clearly,
LHS = RHS
Thus,
Dividend = Divisor×Quotient + Remainder