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 the problem, we'll follow these steps:
Step 1: The quadratic formula yields the roots:
where , , and .
Calculating the discriminant:
.
Since the discriminant is negative (), the quadratic equation has no real roots. This means the parabola does not intersect the x-axis, and the entire graph is above or below it.
Step 2: Since (positive), the parabola opens upwards. A quadratic function with no real roots and a positive leading coefficient will be entirely above the x-axis, indicating it is always greater than zero.
Step 3: Since it is positive across all -values, the solution is:
The function is positive for all .
The function is positive for all .
The graph of the function below intersects the X-axis at points A and B.
The vertex of the parabola is marked at point C.
Find all values of \( x \) where \( f\left(x\right) > 0 \).
A negative discriminant means the parabola never touches the x-axis. It's either completely above or below the x-axis, depending on whether it opens up or down.
Look at the leading coefficient (the number in front of ). If it's positive, the parabola opens upward. If negative, it opens downward.
When a > 0, the parabola opens upward. With no real roots, it never touches the x-axis. Since it opens upward and never touches the x-axis, the entire graph must be above the x-axis!
If with a negative discriminant, the parabola would open downward and never touch the x-axis. This means it would be always negative, so f(x) > 0 would have no solution.
You don't need to finish the quadratic formula calculation! Once you see the discriminant is negative, you know there are no real roots. Just check the leading coefficient to determine the sign.
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