The measurement of angle x is 40°. these two triangle are congruent so their sides share the same length and their angles share the same degrees
He made a mistake in step #2. It seemed to be a trivial mistake because it involved signs, but it still had a great impact. Since step#2, his solution was already wrong.
Instead of
(-1)²-4(2)(-6) = 1 + 48 = 49
What he did is
(-1)²-4(2)(-6) = -1 + 48 = 47
Inverse property of multiplication
(a*1/a=1)
