Answer:
The equation of the sraight line 3x- y+ 6 =0
Step-by-step explanation:
<u><em>Explanation:-</em></u>
Given that the gradient of the function
|gradf| = 3 and point (-1,3)
Given that the slope of the line
m = 3
The equation of the straight line passing through the point(-1,3) and slope m =3

y-3 = 3(x-(-1))
y-3 = 3x+3
3x +3-y+3=0
3x- y+ 6 =0
<u><em>Final answer:-</em></u>
The equation of the sraight line 3x- y+ 6 =0
<u><em></em></u>
Line 1:
slope 2, point(1,8)
hence we have its equation:
y - y1 = m(x - x1)
y - 8 = 2(x - 1)
y = 2x + 6
line 2:
point1(1, 2), point2(2, 1)
hence its slope is:
m = (1 - 2)/(2 - 1) = -1
y - 2 = -1(x - 1)
y = -x + 3
if lines intersect, we can equal both equations and find the point:
y = y
2x + 6 = <span>-x + 3
</span>3x = -3
x = -1
and substitute to find y:
<span>y = -x + 3 = 1 + 3 = 4
</span>therefore the intersection point is (-1, 4), and -1 + 4 = 3