# Algebra 1

posted by on .

write an equation of the line containing the point and perpendicular to the given line (4,-8); 2x+5y=4

I am having a very hard time, but I'm trying hard to study the steps for solving the problem.

Profoundly, thank you.

• Algebra 1 - ,

Post your work so I can see where you are having trouble.

• Algebra 1 - ,

Sorry, but, no, I didn't see the answer to my post. However,

(4,-8); 2x+5y=4 is?

y=-2x+4

y-8=1/2

y-8=1/2(x-4)

Again, I don't really know what to do after this. I may not even be followin the steps right. However, I would really appreacite your help. Thank you a million.

• Algebra 1 - ,

2x + 5y = 4
5y = -2x + 4
divide both sides by 5
y = -2/5 y + 4/5
So, slope m = -2/5

Perpendicular lines, the slopes are negative reciprocals of each other.
Slope = -2/5
m1 * m2 = -1
-2/5 * m2 = -1
m2 = -1/(-2/5)
m2 = 5/2

Now you have to find b, for the equation of the perpendicular line.
y = mx + b
m = 5/2
y = 5/2 x + b
P(4, -8)
-8 = 5/2 (4) + b
-8 = 20/2 + b
-8 = 10 + b
-18 = b

y = 5/2 x + b
y = 5/2 + -18
y = 5/2 - 18