1.

Factorise : 12x^2-7^x+1 using factor theorem

Answer»

Hi,

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Factor Theorem :

If p( x ) is a polynomial of degree n ≥ 1 and

' a ' is any real number , then

i )( x - a ) is a factor of p( x ) , if p( a ) = 0,

ii ) and it's converse " if ( x - a ) is a factor of

a polynomial p( x ) then p ( a ) = 0,

***********"***********************

Now ,

Let p( x ) = 12x² - 7x + 1 ,

= 12x² - 4x - 3x + 1

= 4x ( 3x - 1 ) - 1( 3x - 1 )

= ( 3x - 1 )( 4x - 1 )

TAKE 3x - 1 = 0 or 4x - 1 = 0

x = 1/3 or x = 1/4

p ( 1/3 ) = 12 × ( 1/3 )² - 7 ( 1/3 ) + 1

= 12/9 - 7/3 + 1

= 4/3 - 7/3 + 1

= ( 4 - 7 + 3 )/3

= 0

Therefore ,

x - 1/3 is a factor of p ( x ) .

2 ) p( 1/4 ) = 12 ( 1/4 )² - 7( 1/4 ) + 1

= 12/16 - 7/4 + 1

= 3/4 - 7/4 + 1

= ( 3 - 7 + 4 ) / 4

= 0

Therefore ,

x - 1/4 is a factor of p( x ).

Now , we CONCLUDE that ,

x - 1/3 , x - 1/4 are two FACTORS of p( x ).

I hope this helps you.

: )



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