Advanced Math practice question

Answer: 8

One real solution means the discriminant is zero: 8² − 4(2)(c) = 64 − 8c = 0, so c = 8. (Then 2x² + 8x + 8 = 2(x + 2)².)

Common wrong answers

If you answered 4

4 is c/2 or the number inside (x + 2)² squared; the equation's c is 8.

If you answered 16

16 forgets the coefficient 2 in 4ac: 64 − 4c = 0 gives 16, but the x² coefficient is 2.

If you answered 64

64 is b², not c.

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