Question 986526
Hi there,
First of all rearrange 5x + 8y = -9
into the form:
y = mx + b
5x + 8y = -9
8y = -5x -9
y = -5/8x - 9/8
m is the gradient and equals
here -5/8
b is the y coordinate of the
line's intersection with the 'y' axis.
here -9/8
..................
Lines that are perpendicular to one another
have gradients that multiply together to give -1
m1 x m2 = -1
To find the gradient (m) of line 12
-5/8 x m2 = -1
m2 = 8/5
Now using the line equation:
y - b = m(x - a)
Where m = 8/5
(a,b) -> (10, 10)
y - 10 = 8/5(x - 10)
y - 10 = 8/5x - 80/5
y = 8/5x - 80/5 + 50/5 (10)
y = 8/5x - 30/5......this is line 12
Now you can report that m = 8/5
and b = -30/5
m + b
So 8/5 + (-30/5) = -22/5
Hope this helps :-)