<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.
A) -4/3
B) -5/4
C) 3/4
d) 5/4
E) 4/3</p>
<p>The answer is A, can anyone tell me how to do this prob?</p>
<p>Also this one:</p>
<p>Let the function f be defined by f(x)= x+1
If 2f(p)=20, what is the value of f(3p)?</p>
<p>Okay, so here we go </p>
<p>y = -4x +k --> Perpendicular--> y = (1/4)x + b</p>
<p>sub in zero in the perpendicular eq to get b = 0 so final perpendicular equation is:
y = (1/4)x</p>
<p>now plug in (t+1,t) and you have the answer</p>
<p>t+1 = t/4</p>
<p>4t+4 = t
3t= -4
t= -4/3</p>
<p>y=-4x+k
The slope of the perpendicular line is 1/4
y=1/4x
t+1=t/4
solve for t
The answer is -4/3 A.</p>
<p>nice shiomi... but a millisecond too slow</p>
<p>Finally, I can contribute to something:</p>
<p>Let the function f be defined by f(x)= x+1 If 2f(p)=20, what is the value of f(3p)?</p>
<p>2(x+1)=20
2x+2=20
-2 -2
2x=18
x=9 </p>
<p>f(27)=27+1
28:Answer</p>
<p>t+1=t/4
How could you get that?
Oh, I got it. Please correct me if my thinking is amiss:
because the two lines meet at one place, we have the equation of:
-4x +k =1/4x
<=> y=y
<=>t+1=1/4 * t
<=> t+1= t/4
right?</p>