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Find the value of a, if the division of ax3 + 9x2 + 4x – 10 by x + 3 leaves a remainder 5.

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Question

Find the value of a, if the division of ax3 + 9x2 + 4x – 10 by x + 3 leaves a remainder 5.

Sum
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Solution

Let f(x) = ax3 + 9x2 + 4x – 10

x + 3 = 0

`\implies` x = –3 

On dividing f(x) by x + 3, it leaves a remainder 5. 

∴ f(–3) = 5 

a(–3)3 + 9(–3)2 + 4(–3) – 10 = 5

–27a + 81 – 12 – 10 = 5

-27a + 81 - 22 = 5

-27a + 59 = 5

-27a = 5 - 59

-27a = -54

a = `(-54)/-27`

a = 2

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Chapter 8: Factorization of Polynomials (Remainder and Factor Theorems) - Exercise 8 (A) [Page 109]

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Selina Concise Mathematics [English] Class 10 ICSE
Chapter 8 Factorization of Polynomials (Remainder and Factor Theorems)
Exercise 8 (A) | Q 10. | Page 109

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