SOLUTION: Let line l1 be the graph of 5x + 8y = -9. Line l2 is perpendicular to line l1 and passes through the point (10,10). If line l2 is the graph of the equation y=mx +b, then find m+b.

Question 1015739: Let line l1 be the graph of 5x + 8y = -9. Line l2 is perpendicular to line l1 and passes through the point (10,10). If line l2 is the graph of the equation y=mx +b, then find m+b.
Answer by macston(5194) (Show Source): You can put this solution on YOUR website!
Find slope of first line (slope-intercept form):
.
5x+8y=-9
8y=-5x-9
y=-(5/8)x+(9/8)
m=-5/8
.
Slope of perpendicular line is negative reciprocal of original.
Slope line 12=m=8/5
.
In slope intercept form:
y=mx+b
y=(8/5)x+b
.
To find b, use given point (10,10)
x=10; y=10
.
y=(8/5)x+b
10=(8/5)(10)+b
10=(80/5)+b
10=16+b
-6=b
.
ANSWER: m=8/5; b=-6; m+b=-22/5
.

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