Step 2: She did not simplify under the square root correctly
under the square root:
(-6)^2 =36
and -4(5)(-8) =160
therefore under the square root it needs to be square root of 36+160 which is square root of 196.
That answer is 14 when square rooted
Y=11x+2 should be you answer for the slope
Recall your d = rt, distance = rate * time
one car is going at 55kph, at say hmmm "t" time
the second car zooms by at 75kph, an hour later, thus " t + 1 "
notice, overtaking the 1st car, simply means, the second car comes from behind approaches the first car from behind and "gets there", at that very second, both cars have travelled a distance, say "d"
if the first car travelled "d" kilometers
for the second car to "get there" has to had travelled "d" distance as well

solve for "t"
y-intercept -3
slope 1/2
is sufficient info with which to write an equation for a straight line:
y = mx + b becomes y = (1/2)x - 3.
You should check this by determining whether or not (2,-1) satisfies this equation.