math help please??

Question

two perpendicular lines intersect on the x-axis. One line has the equation y=-3/4+3. What is the equation of other line.

- i know that the slope is just reciprical, but what about y-intercept??

Answer 1

the lines intersect on the x axis
so obviously the y coordinate of the point of intersection is 0
by substituting 0 in the given equation x coordinate can also be calculated.
now u assume the other line is y= mx + c. u know the gradient (m)of the line and a point on the line.
so you can now calculate the y intercept.
do it urself

Answer 2

heres how you do it

since it tells you where it intersects. (on the x axis)
you plug 0 in for y in the first equation and get the coordinates of the intersection point

you then use the slope (the reciprocal of the original) and plug in the coordinates you found for the intersection to solve for the intercept.


Here's a better explanation:

You know that every line has the general equation:
y = mx + b

The first equation is:
y = (-3/4)x + 3

so, it tells you that the intersection of both lines in ON the x-axis
That means they intersect when the y value is 0
y = 0

so you plug that into the first equation:
0 = (-3/4)x + 3
now solve for x
x = 4

So, to find the equation of the second line, you know that it is perpendicular.
So you know that the slope, m = 4/3

so you have the general equation:
y = (4/3)x + b

And since you know the coordinates of the intersection point (4,0)
you plug that in and solve for the y intercept, b
0 = (4/3)(4) + b
b = -16/3

So the equation of the second line is:
y = (4/3)x - 16/3

Answer 3

y= (-3/4) x+3

this line intersect x on the abcissa corresponding to y=0

0= 3 -(3/4) x ---> x=4

the slope of the other line is m = -1/(-3/4) = 4/3

so ,you know that this line has the form y' = 4/3 x+b (1)

and intersect at y=0 , x=4 substitutein (1)

0 = (4/3 ) 4 +b b =-16/3

the lign is y' = (4/3)x -16/3

Answer 4

I assume the equation is y = -3/4x + 3
this line crosses the x-axis where y = 0, so:
0 = -3/4x + 3
3/4x = 3
x = 4

So both lines go through point (4,0)

for your second line, you know the slope (4/3, the negative reciprocal of -3/4) and a point (4,0) so we need to calculate b:

y = 4/3x + b
0 = 4/3(4) + b
0 = 16/3 + b
b = -16/3

y = 4/3x - 16/3

Hope this helps! :)

Answer 5

so you already know the slope so the other line is

y=4/3x+b

plug in a point on the line to solve for b.

you know that they share the same x intercept so... just plug in 0 for y in the other equation to get x. then plug this point back in to the y=4/3x +b to solve.