Given that f: x --> x\(^2\) - x + 1 is defined on the Set Q = { x : 0 ≤ x < 20, x is a multiple of 5}. find the set of range of F.

  • A {21, 91, 221}
  • B {21, 91, 221, 381}
  • C {1,21, 91, 221}
  • D {1,21, 91, 221,381}
waec 2021furthermathematics

The correct answer is A. {21, 91, 221}

multiples of 5 less than 20 = 5, 10 and 15

= [ 5, 10 and 15 ]x\(^2\) - x + 1

x\(^2\) - x + 1

when x = 5

5\(^2\) - 5 + 1; 25 - 5 + 1 --> 21

when x = 10

10\(^2\) - 10 + 1

100 - 9 = 91

when x = 15

15\(^2\) - 15 + 1

225 - 15 + 1 = 211

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