Mathematics for IGCSE & O level - Surds (Section 2 - No. 24)

If x = 4 + √7, what is x^2 - 8x + 9?

16

23

9

1

Explication

x^2 - 8x + 9 = (4+√7)^2 - 8(4+√7) + 9 = (16+8√7+7) - 32 - 8√7 + 9 = 23

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