Look at the following function:
Determine for which values of the following is true:
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Look at the following function:
Determine for which values of the following is true:
To solve this problem, we'll follow these steps:
Now, let's work through each step:
Step 1: The quadratic function has a leading coefficient , which is negative. This indicates that the parabola opens downwards, potentially sitting below the -axis.
Step 2: Calculate the discriminant .
Here, , , and . Plug these into the formula:
Since the discriminant is negative, there are no real roots. The parabola does not intersect the -axis.
Step 3: Discuss implications.
Because the parabola opens downward and has no real roots, it lies entirely below the -axis. This means for all real values of , .
Therefore, the function is negative for all .
The function is negative for all .
The function is negative for all .
The graph of the function below does not intersect the \( x \)-axis.
The parabola's vertex is marked A.
Find all values of \( x \) where
\( f\left(x\right) > 0 \).
A negative discriminant means the quadratic has no real roots - the parabola never touches or crosses the x-axis. It stays entirely above or below the x-axis.
Check the leading coefficient! If a > 0 and no real roots, the parabola opens up and stays above x-axis (always positive). If a < 0 and no real roots, it opens down and stays below x-axis (always negative).
You could test a value, but using the discriminant method is more reliable and complete. It tells you definitively about the entire function, not just one point.
If , the parabola would have two real roots and cross the x-axis twice. Then you'd need to find those roots to determine where f(x) < 0.
Absolutely! Completing the square for gives . Since the maximum value is -2, the function is indeed always negative.
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