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| Math Central | Quandaries & Queries |
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Question from Pranav, a student: If ax^2+bx-5=0 has no real roots. Then d sign of 1) a+b-5 |
Hi Pranav,
Let $f(x) = a x^2 + b x - 5$ and notice that $f(0) = -5.$ Think of the graph of $y = f(x).$ Since $f(x) = 0$ has no real roots the graph does not cross the X-axis. But at $x = 0$ the point on the graph is below the X-axis so the entire graph is below the X-axis.
What is $f(1)?$
Penny
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