Example Divide x5 + 243 by x + 3
Solution: Write the dividend in the coefficient form, and write -3 to the left of the 1st coefficient
\ x5 + 243 = ( x + 3 ) ( x4 - 3x3 + 9x2 - 27x + 81 ) + 0
FACTORING :
Factor : When a number or an expression is the product of two or more numbers or expressions, each of the latter is called a factor of the former. Thus 4 and 7 are factors of 28 and ( x + y ) and ( x - y ) are factors of x2 - y2.
Factoring or factorization is the process of changing any algebraic or numerical expression from a sum of terms into a product of factors. A number or expression is said to be prime if no factors can be obtained of that.
1. Expressions in which each term has a common factor.
We have seen that x ( a + b + c ) = x a + x b + x c.
We write this as x a + x b + x c = x ( a + b + c ) . ® ( 1 )
(1) shows that x and ( a + b + c ) are factors
x a + x b + x c .
Here we notice that every term on L. H. S. of (1)
contains x as a factor. The other factor ( a + b + c ) can be obtained
by dividing the given expression x a + x b + x c by the common factor
x .
Example Factorise 5x3
+ 7x
Solution: 5x3 + 7x = x
(5x2 + 7 )
Example Find the factor of ap - aq + a r
Solution: ap - aq + a r = a ( p - q + r )
Example Factorise 2m3 + 8m2 + 10m
Solution: 2m3 + 8m2 + 10m = 2m
( m2 + 4m + 10 )
Example Find the factors of 2a3b - 8a2b2
Solution: 2a3b - 8a2 b2
= 2a2 b ( a - 2b )
Example Factorise c ( a + b ) + d ( a + b ) + e ( a +
b )
Solution: c ( a + b ) + d ( a + b ) + e ( a + b ) =
( a + b ) ( c
+ d + e )
2. Factors by arranging terms in suitable groups.
Example Factorise ac + bc + bd + ad + ae + be
Solution: Here we cannot find a common factor. We can
form suitable groups, thus expression
= ( ac + bc ) + ( ad + bd ) + ( ae + be )
= c ( a + b ) + d ( a + b ) + e ( a +
b )
= ( a + b ) ( c + d + e )
or expression
= ( ac + ad + ae ) + ( bc + bd + be )
= a ( c + d + e ) + b ( c + d + e )
= ( c + d + e ) ( a + b )
= ( a + b ) ( c + d + e )
Example Resolve into factors x3 + 2x2y
- 2xy2 - 4y3
Solution: x3 + 2x2y - 2xy2
- 4y3 =
= x2( x + 2y ) - 2y2 ( x + 2y )
= ( x + 2y ) ( x2 - 2y2 )
Example ax - ay - bx + by + cx - cy
Solution: expression =
= a ( x - y ) - b ( x - y ) + c ( x - y )
= ( x - y ) ( a + b + c )
Perfect squares i) ( a + b )2 = a2 + 2 ab + b2 ii) ( a - b )2 = a2 - 2 ab + b2
3. Factors of expression of the form.
a2 + 2 ab + b2 = ( a + b )2 ..... (1)
a2 - 2 ab + b2 = ( a - b )2 ......(2)
Example Factorize x2 + 4x + 4
Solution: x2
+ 4x + 4=
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