Sum
If (x – 2) is a factor of the expression 2x3 + ax2 + bx – 14 and when the expression is divided by (x – 3), it leaves a remainder 52, find the values of a and b
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Solution
Since (x-2) is a factor of polynomial `2x^3+ax^2+bx-14`, we have
`2(2)^3+a(2)^2+b(2)-14=0`
⇒ `16+4a+2b-14=0`
⇒`4a+2b+2=0`
⇒`2a+b+1=0`
⇒`2a+b=-1` .............(1)
On dividing by (x-3), the polynomial `2x^3+ax^2+bx-14` leaves remainder 52,
⇒`2(3)^3+a(3)^2+b(3)-14=52`
⇒`54+9a+3b-14=52`
⇒`9a+3b+40=52`
⇒`9a+3b=12`
⇒`3a+b=4` ...............(2)
Subtracting (1) and (2), we get
a=5
substituting a =5 in (1), we get
`2xx5+b=-1`
⇒`10+b=-1`
⇒`b=-11`
Hence , a=5 and b=-11.
Concept: Remainder Theorem
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