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What number should be subtracted from x3 + 3x2 – 8x + 14 so that on dividing it by x – 2, the remainder is 10? - Mathematics

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Question

What number should be subtracted from x3 + 3x2 – 8x + 14 so that on dividing it by x – 2, the remainder is 10? 

Sum

Solution

Let the number to be subtracted be k and the resulting polynomial be f(x). 

So, f(x) = x3 + 3x2 – 8x + 14 – k 

It is given that when f(x) is divided by (x – 2), the remainder is 10. 

∴ f(2) = 10   

(2)3 + 3(2)2 – 8(2) + 14 – k = 10 

8 + 12 – 16 + 14 – k = 10 

18 – k = 10

– k = 10 – 18 = – 8

k = 8 

Thus, the required number is 8.

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

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Selina Mathematics [English] Class 10 ICSE
Chapter 8 Remainder and Factor Theorems
Exercise 8 (A) | Q 14 | Page 109

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