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If 3 and –3 are two zeroes of the polynomial (x^4 + x^3 – 11x^2 – 9x + 18), find all the zeroes of the given polynomial.

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प्रश्न

If 3 and –3 are two zeroes of the polynomial (x4 + x3 – 11x2 – 9x + 18), find all the zeroes of the given polynomial.

योग
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उत्तर

Let x4 + x3 – 11x2 – 9x + 18

Since 3 and –3 are the zeroes of f(x), it follows that each one of (x + 3) and (x – 3) is a factor of f(x).

Consequently, (x – 3) (x + 3) = (x2 – 9) is a factor of f(x).

On dividing f(x) by (x2 – 9), we get:   

`x^2 - 9")"overline(x^4 + x^3 - 11x^2 - 9x + 18)"("x^2 + x - 2`
            x4             – 9x2
            –               +                          
           x3 – 2x2 – 9x + 18
           x3           – 9x
           –              +                           
                        –2x2 + 18
                        –2x2 + 18
                        +       –                    
                             x                        

f(x) = 0 ⇒ (x2 + x – 2) (x2 – 9) = 0

⇒ (x2 + 2x – x – 2) (x – 3) (x + 3)

⇒ (x – 1) (x + 2) (x – 3) (x + 3) = 0

⇒ x = 1 or x = –2 or x = 3 or x = –3

Hence, all the zeroes are 1, –2, 3 and –3.

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अध्याय 2: Polynomials - EXERCISE 2B [पृष्ठ ६३]

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आर.एस. अग्रवाल Mathematics [English] Class 10
अध्याय 2 Polynomials
EXERCISE 2B | Q 15. | पृष्ठ ६३

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