factorise x^3-13x-12 use factor theorem
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→ p( x ) = x³ - 13x - 12
=> p( -1 ) = ( -1 )³ - 13( -1 ) -12
=> p( -1 ) = -1 + 13 - 12 = 0
=> By Remainder / Factor theorem, ( x - [ -1 ] ) is a factor
=> p( x ) = ( x + 1 )( x² - x - 12 )
• p( -3 ) = ( -3 + 1 )( 9 - ( -3 ) - 12 ) = ( -2 )( 0 ) = 0
• p( 4 ) = ( 4 + 1 )( 16 - 4 - 12 ) = 5 x 0 = 0
=> p( x ) = ( x + 1 )( x + 3 )( x - 4 )
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Let, the given polynomial be
NOW, WE WILL substitute various values of x until we get p(x)=0 as follows:
[/tex]
THUS, (x-4) is a factor of p(x)
now,
p(x)=(x-4)×g(x)...............(I)
Therefore, g(x) is obtained by after dividing p(x) by (x-4) as shown attachment:
From the division, we get the quotient
and now we factorise it as follows:
from eq.(I), we get p(x)=(x-4)(x+3)(x+1)
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