Look at the function shown in the figure.
When is the function positive?
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Look at the function shown in the figure.
When is the function positive?
The function we see is a decreasing function,
Because as X increases, the value of Y decreases, creating the slope of the function.
We know that this function intersects the X-axis at the point x=-4
Therefore, we can understand that up to -4, the values of Y are greater than 0, and after -4, the values of Y are less than zero.
Therefore, the function will be positive only when
X < -4
Look at the function shown in the figure.
When is the function positive?
Look at the graph direction! Since this line slopes downward (decreasing), the function is positive to the left of the x-intercept at x = -4.
The line crosses the x-axis at x = -4. For a decreasing function, values are positive before the intercept and negative after. So x < -4 gives positive y-values.
A function is positive when its y-values are greater than zero. On a graph, this means the line is above the x-axis.
Pick a test point! Choose x = -5 (which is < -4). If the function gives a positive y-value at x = -5, then is correct.
Yes! For decreasing functions, positive regions are typically where x is less than the x-intercept. For increasing functions, it's usually where x is greater than the intercept.
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