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Question

When Scott completes the square on the quadratic x^2 + 8x - 1 = 0, he obtains an equation of the form (x + a)^2 = b. What is b?

Accepted Answer

We can square x + 4 to get x^2 + 8x + 16, so the given equation becomes x^2 + 8x - 1 = (x^2 + 8x + 16) - 16 - 1 = (x + 4)^2 - 17 = 0, which means (x + 4)^2 = 17. We see that b = 17.