Explanation:
15.
D (2, -9), simply because it is the only point in the answer options that is on the curve (when you put x into the equation, y has to be the result - only for D possible).
16.
(7 + 2i)(4 - 5i) = 28 - 35i + 8i - 10i² = 28 - 27i + 10 =
= 38 - 27i
C.
17.
A.
-10 + 4 = -6
that defines the middle factor (-6x).
18.
for a quadratic equation
ax² + bx + c = 0
the solution is
x = (-b ± sqrt(b² - 4ac))/(2a)
the discriminant is the argument of the square root :
b² - 4ac
in our case that is
14² - 4×3×8 = 196 - 96 = 100
19.
C.
(15 - 9i) - (23 - 14i) = 15 - 9i - 23 + 14i = -8 + 5i
20.
the solution is as described in 18.
x = (-6 ± sqrt(6² - 4×1×14))/(2×1) =
= (-6 ± sqrt(36 - 56))/2 = (-6 ± sqrt(-20))/2 =
= (-6 ± sqrt(-4×5))/2 = (-6 ± 2i×sqrt(5))/2 =
= -3 ± i×sqrt(5)
D.
21.
C.
-10 + 1 = -9
that defines the middle factor (-9x).
22.
(x + 2)² = 36
x + 2 = ±6
x + 2 = 6
x = 4
x + 2 = -6
x = -8
A.