If x = 9, then the value of x5 - 10x4 + 10x3 - 10x2 + 10x - 1 is:
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 8
Given:
x = 9
Explanation:
Sunstituting x = 9 in x5 - 10x4 + 10x3 - 10x2 + 10x - 1
⇒ 95 - 10(9)4 + 10(9)3 - 10(9)2 + 10(9) - 1
Write 10 = (9 + 1) in the above equation,
⇒ 95 - (9 + 1)(9)4 + (9 + 1)(9)3 - (9 + 1)(9)2 + (9 + 1)(9) - 1
⇒ 95 - 95 - 94 + 94 + 93 - 93 - 92 + 92 + 9 - 1
⇒ 9 - 1 = 8
Hence the required answer is 8.