Respuesta :
Answer:
x = - 3
Step-by-step explanation:
x² - 21 = 4x
x² - 4x - 21 = 0
(x + 3) (x - 7) = 0
x = -3 or x = 7
The negative value is -3.
How the negative value is -3?
Given that, 21 is subtracted from the square of a number.
Based on the given condition,
x² - 21 = 4x
x² -21 -4x = 0
x² - 4x - 21 = 0
x² - 7x + 3x - 21 = 0
x(x - 7) + 3(x - 7) = 0
(x - 7) (x + 3) = 0
x - 7 = 0 or x + 3 = 0
x = 7 0r x = -3
The negative solution = -3.
Learn more about subtraction from a square number, refer:
https://brainly.com/question/10844866
#SPJ2
