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If x (x – 3) = – 1, then the value of x³(x³ - 18) is

1. – 1
2. 2
3. 1
4. 0

Correct Option: A

x (x – 3) = –1
⇒ x² – 3x = –1
⇒ x² – 3x + 1 = 0
Expression = x³( x³ - 18 ) = x⁶ - 18x³
On dividing ( x⁶ - 18x³ ) by ( x² – 3x + 1 )

∴ x⁶ - 18x³ = (x⁴ + 3x³ + 8x² + 3x)
( x² – 3x + 1 ) + x² – 3x
= 0 + x (x – 3) = –1