50
For any real number x, the maximum value of 4 – 6x – x2 is
- A4
- B7
- C9
- D13
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Discussion 1
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CCommunity
(a + b)2 = a2 + b2 + 2ab
4 – 6x – x2
= 4 – (6x + x2)
= 4 + 9 – (x2 + 6x + 9)
= 13 – (x + 3)2
Thus the maximum value will be obtained when (x + 3)2 is zero
The maximum value is 13
4 – 6x – x2
= 4 – (6x + x2)
= 4 + 9 – (x2 + 6x + 9)
= 13 – (x + 3)2
Thus the maximum value will be obtained when (x + 3)2 is zero
The maximum value is 13