Answer:
The values of x and y are x = -3 and y = -2
Step-by-step explanation:
In the complex numbers if a + bi = c + di, then the real parts are equal and the imaginary parts are equal
Let us use this rule to solve the question
∵ -21 + 5yi = 7x - 10i
∴ The real parts are -21 and 7x
∴ The imaginary parts are 5y and -10
∵ The real parts are equal
∴ 7x = -21
→ Divide both sides by 7
∴
= 
∴ x = -3
∵ The imaginary parts are equal
∴ 5y = -10
→ Divide both sides by 5
∴
= 
∴ y = -2
∴ The values of x and y are x = -3 and y = -2
C I’m pretty sure, if wrong I’m sorry
Answer:

Step-by-step explanation:
To evaluate
from the following expression:

Taking 


∴ 
Answer:
4
Step-by-step explanation:
ΔABC is congruent with ΔDEF. That means the corresponding sides are congruent.
Look at the order of the letters. EF are the last two letters of ΔDEF. So this corresponds with the last two letters of ΔABC. Therefore, EF ≅ BC.
EF ≅ BC
x² + 8x = 48
x² + 8x − 48 = 0
(x + 12) (x − 4) = 0
x = -12 or 4
Since x can't be negative, x = 4.