<p>In the xy plane, line l passes through the origin and is perpendicular to the line 4x+y=k, where k is a constant. If the two lines intersect at the point (t,t+1). What is the value of t?
This is a level five question. Please help me in it. Thx</p>
<p>Have you tried searching this … site? This problem must have been solved and explained a few times. </p>
<p>Check terms such as slope and planes.</p>
<p><a href=“http://talk.collegeconfidential.com/sat-preparation/195443-hard-math-problems-need-some-help.html[/url]”>http://talk.collegeconfidential.com/sat-preparation/195443-hard-math-problems-need-some-help.html</a>
1st question in this thread, search google and you’ll get results from yahoo answers and other places too ;)</p>
<p>This is not a hard question if you know the formula
Line l: y=ax+b
line d: 4x + y = k or y = -4x + k
Line (l) is perpendicular to line (d) so the slope of line (l) or the value of a is (-1)/(-4) = 1/4 = 0.25
So now we have line l: y= 0.25x + b.
Because line l passes through the origin (0,0): 0 = 0.25 x 0 + b <=> b= 0.
Then we have line l: y = 0.25x.
Line (l) and line (d) intersects at the point P (t, t+1) => Line (l) passes through point P
=> t+1 = 0.25 x t <=> t=-4/3</p>
<p>Hope this helps</p>