(b) find all 3-tuples (a, b,c) satisfying
a[1,-1,0,0]+b[0,1,-1,0]+c[0,0,1,-1] =0
(theses are all 1x4 matrices)

We have a three unknown, 4 equation homogeneous system.  These always have at least (0,0,0) as a solution.  Let's write the equations, one column at a time.

1a + 0b + 0c = 0

-1a + 1b +0c = 0

0a - 1b + c = 0

0a + 0b + -1 c = 0

We could do row reduction but these are easy enough not to bother.

Equation 1 says

a = 0

Equation 4 says

c = 0

Substituting in the two remaining,

-1(0) + 1b + 0c = 0

b = 0

0(0) - 1b + 0 = 0

b = 0

The only 3-tuple satisfying the vector equation is (a,b,c)=(0,0,0)

y = 5x + 17

step-by-step explanation:

a perpendicular line will be the opposite reciprocal slope of the given equation.   the slope given is -1/5 so the opposite reciprocal is 5

find b:

7 = 5 (-2) + b

7 = -10 + b

17 = b

write equation

y = 5x + 17

answer: the distance

step-by-step explanation:

to calculate the distance d of a line segment with endpoints (x1, y1) and (x2, y2) use the formula d (x2 x1)2 (y2 y1)2. to calculate the midpoint of a line segment with endpoints (x1, y1) and (x2, y2) use the formula