<p>For some reason, I don't remember how to solve this:</p>
<p>In the xy-coordinate plane, line m is the reflection of line l abou the x-axis. If the slope of line m is -4/5, what is the slope of line l?</p>
<p>(A) 5/4
(B) 4/5
(C) 1/5
(D) -4/5
(E) -5/4</p>
<p>(answer is B, but why?)</p>
<p>Draw it out as Y=-4/5X, and then you could do Y=5/4X, etc. for all answer choices, or see that the line would simply go from being negative to positive (All Y-values flip), so the slope goes from negative to positive.</p>
<p>Choose some "easy" line m with the slope -4/5, such as Eloquence eloquently suggested :), y=(-4/5)x .</p>
<p>It goes through (0, 0) and (5, -4).
Reflection of (5, -4) about the x-axis is (5, 4), so line l (reflection of line m about the x-axis) goes through (0, 0) and (5, 4).
That gives you a slope 4/5 for l.</p>
<p>What happens with the slope when you reflect line m about the y-axes?
about y=-x? about y=x?
The same approach would work.</p>
<p>t h a n k s</p>
<p>for any line of reflection do you just change the sign of the slope?</p>
<p>no, this one was specifically reflected across the x axis.</p>
<p>if it's reflected across the y-axis, you change the x-values. </p>
<p>if it's reflected across the origin, you change both values.</p>
<p>yea- just know that hwen it is reflected across the x, you negate the y, and when you relect across teh y, you change the x. so if you have y=-4/5x, and that is reflected back across teh x axis, then you just negate the y, and you get -y=-4/5x, which is equal to y=4/5x. YEA!</p>
<p>What gcf said.</p>
<p>oh my bad i didnt read it. SORRY</p>