Which point is an x-intercept of the quadratic function f(x) = (x - 4)(x + 2)?
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Answer:
see attached
Step-by-step explanation:
<u>boundary line</u>
When graphing, it can be useful to have the equation in slope-intercept form. You can get that by solving for y.
4y ≤ -5x -4 . . . . subtract 5x from both sides
y = -5/4x -1 . . . . divide both sides by 4
This tells you the slope is -5/4, and the boundary line crosses the y-axis at y = -1. The slope is the ratio of rise to run, so -5/4 tells you the line will go down 5 units for each 4 unit to the right. That is, points (4, -6) and (-4, 4) will be on the line.
<u>line type and shading</u>
The "or equal to" part of the inequality symbol (≤) tells you that the boundary line will be solid, not dashed.
The "less than" part of the symbol tells you that the values of x and y are less than those on the boundary line, so shading will be to the lower-left. The graph is shown in the attachment.
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<em>Additional comment</em>
You can determine the location of the shading by looking at any variable term that has a positive coefficient, and its relation to the inequality symbol. Here, that could be either of ...
- 5x ... ≤ ...
- 4y ... ≤ ...
These tell you that x- and y-values in the solution set are less than those on the line, so shading will be left of (x<) or below (y<) the line. (In rare cases where all of the variable coefficients are negative, you can multiply the equation by -1 and reverse the inequality before you make this analysis.)
