The 2 angles are complemantary or form right angles so

so

. Plugging that into BDC we get 11
(a-b)^2 = a^2-2ab+b^2
(8-5i)^2 = 8^2-2(8)(5i)+(5i)^2
= 64-80i+25i^2
i^2=-1
So
= 64-80i+25(-1)
=64-25-80i
= <em><u>39 - 80i</u></em>
which is your answer :)
A, the first choice. c doesn't say tht its in a logical flow
Question 14, Part (i)
Focus on quadrilateral ABCD. The interior angles add to 360 (this is true for any quadrilateral), so,
A+B+C+D = 360
A+90+C+90 = 360
A+C+180 = 360
A+C = 360-180
A+C = 180
Since angles A and C add to 180, this shows they are supplementary. This is the same as saying angles 2 and 3 are supplementary.
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Question 14, Part (ii)
Let
x = measure of angle 1
y = measure of angle 2
z = measure of angle 3
Back in part (i) above, we showed that y + z = 180
Note that angles 1 and 2 are adjacent to form a straight line, so we can say
x+y = 180
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We have the two equations x+y = 180 and y+z = 180 to form this system of equations

Which is really the same as this system

The 0s help align the y terms up. Subtracting straight down leads to the equation x-z = 0 and we can solve to get x = z. Therefore showing that angle 1 and angle 3 are congruent. We could also use the substitution rule to end up with x = z as well.
5/9 * 2*5+4/5
5/9 * 10 + 4/5
5/9 * 14/5
5 * 14/9 * 5
70/9*5
70/45
14/9
1 5/9.