Need help with this math problem! (this is like my last question)?

Question

Thanks 4 ev1's help on my last Question! They helped A LOT! *Paul W*

this problem is like the last one but its in a differnt form that i cant figure out....



Write the equation of the line, in slope intercept form, that contains the point (-9,9) and is perpendicular to the line 4x + 2y = -7.



It would really help if you could show all of your work... so i can figure out how to do the problem (like i did the last one)

Thanks again 4 ur help!

4 the guy who thinks im just tryn 2 BS people/ thats not true! i hav a test coming up and im trying to learn how to do this stuff... its not even homework (its not worth anything) im just trying to figure this out! Im not using anyone

Answer 1

there are 2 clues on solving this problem
1. The line is perpendicular with another line (it makes a right angle with another line)
2. It passes through a known point.

With clue 1, we are reminded by the properties of perpendicular lines, which is, the gradients of the two lines, when multiplied makes -1.

So what's the gradient? Ok, to convert an function to its slope intercept form (which is the simplest form that shows the gradient explicitly), we just need to make the one of the side of the equation, usually the Left Hand Side, a single y, and no other y on the other side. (y = ...) And see if it fits the common form for slope intercept form, which is y=mx + c. Then take the gradient (m) from the equation, ignore the c and the x, we just need the gradient.

in this problem, we'd get [I'll skip the easy algebra parts]:
4x + 2y = -7
y = -2 x -(7/2)

so the gradient is -2

Now, this is the first line's gradient, and your line is perpendicular to this line. We know that the product of the gradients of two perpendicular lines would make a -1. So:

[-2] * m = -1 << where m is the gradient for your line.
m = -(1/2)

Ok, now we know the gradient of the equation, the next step is easy. Just plug in the gradient into the common form (preferably the slope intercept form).

y = [-(1/2)]x + c

This function is still incomplete, we still don't know the c yet. It's easy to find the c out, since we already know that the line passes through a known point (9, -9), then this points would have satisfied the equation if it's plugged into the incomplete equation.

[9] = -1/2 * [-9] + c
c = 9/2

Ok, now we know the c, just plug it into the function again.

y = -2x + [9/2]

Answer 2

Lol, well I got part of it. The slope intercept form is y=(-4x-7)/(2) so this means that the regular perpendicular function is f(x)=(4x-7)/(2). Now to get it to intersect at -9,9. Im not to sure how to get that. Im in Calc now but I cant reach far enough back into my brain to remember this. Oh, and to get the spi you subtract 4x and divide by 2. Then you just get xy coordinates for the equation and there you go.

Answer 3

Ok, here's how you do problems like this one.

First convert 4x + 2y= -7 to slope intercept form. You should get
y= -2x - 7/2

Now you need it to be perpendicular to this line. That means that the slope needs to be an opposite reciprocal to the slope in the above problem, -2.

y= -1/2x - 7/2

Now, the y intercept, -7/2, won't be the same as the answer.

y= -1/2x + b

Now you plug in (-9,9) and solve for b.

9= -9/2 + b

27/2= b

So, y= -1/2x + 27/2

Answer 4

first write line in slope-intercept form:
4x + 2y = -7
2y = -4x - 7
y = -2x - 7/2
slope of line sought is 1/2 (negative reciprocal)
line goes through (-9,9), so 9 = 1/2 (-9) + b
b = 9 + 9/2 = 27/2
Full equation of line is
y = 1/2 x + 27/2

Answer 5

OK...HInt.

use(rearrange) that equation to write y in terms of x.

then use this y = mx+b, where m is the slope

since perpendicular, take the negative reciprocal, (eg. if its 2, neg rec would be -1/2)

so thats your slope for the new line

then use the formula m = (y2 - y1)/(x2-x1), where ( x1, y1) is your point

clear?

Answer 6

lame kid, do your own homework and don't BS people about "so i can figure out how to do the problem (like i did the last one)" we know you didn't do anything but copy down the last one.

I mean honestly, if you think we're stupid enough to fall for this, then why ask us to do your homework for you?

Answer 7

You're so chicky!
If you need help and not the solution, study the lesson first.

Answer 8

ummmmm................. no