SOLUTION: In the xy plane, the point (-1,2) is the minimum of the quadratic function f(x)=x^2+ax+b. What's the absolute value of a-2b?

Question 1088882: In the xy plane, the point (-1,2) is the minimum of the quadratic function f(x)=x^2+ax+b. What's the absolute value of a-2b?
Found 3 solutions by Fombitz, MathTherapy, ikleyn:
Answer by Fombitz(32388)   (Show Source): You can put this solution on YOUR website!
If it's the minimum value, then it's the vertex.

So then,

Answer by MathTherapy(10552)   (Show Source): You can put this solution on YOUR website!
In the xy plane, the point (-1,2) is the minimum of the quadratic function f(x)=x^2+ax+b. What's the absolute value of a-2b?

Correct answer: , since the question asks for the ABSOLUTE VALUE of a - 2b.
a - b = - 4, but |a - 2b| = 4.
Answer by ikleyn(52781)   (Show Source): You can put this solution on YOUR website!
.
If it's the minimum value, then it's the vertex.

So then a = 2, b = 3

a - 2b = 2 - 2*3 = 2 - 6 = -4.

Absolute value of (a-2b) is 4.

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