18) the answer is 3 because CD is a segment bisector that seperates both AB and BD into 2 congruent segments.And perpendicular lines form right angles.
19) the answer is 1 because the S represents AB is congruent to BD. Then, A represents the right angles: angle ADC and angle BDC. Lastly. S is represented by the common side which is segment CD.
Answer:
(x, y) = (- 2, 5)
Step-by-step explanation:
given the 2 equations
3y = 11 - 2x → (1)
3x = y - 11 → (2)
Rearrange (2) expressing y in terms of x
add 11 to both sides
y = 3x + 11 → (3)
Substitute y = 3x + 11 into (1)
3(3x + 11) = 11 - 2x
9x + 33 = 11 - 2x ( add 2x to both sides )
11x + 33 = 11 ( subtract 33 from both sides )
11x = - 22 ( divide both sides by 11 )
x = - 2
Substitute x = - 2 in (3) for corresponding value of y
y = (3 × - 2) + 11 = - 6 + 11 = 5
As a check
substitute x = - 2, y = 5 into (1) and (2) and if the left side equals the right side then these values are the solution.
(1) : left side = (3 × 5) = 15
right side = 11 - (2 × - 2) = 11 + 4 = 15 ⇒ left = right
(2) : left side = (3 × - 2 ) = - 6
right side = 5 - 11 = - 6 ⇒ left = right
solution = (- 2, 5 )
You are right. In circle equation we have =r² so the correct answer will be C od D. But we have to calculate the center of a circle.

Complete the square:

And we have:

So the answer is C (the same left side of equation).