Ok if I directly write the equation it will become difficult to understand , so I am dividing into small parts. :)
[tex] \\ \\ [/tex]
Let :-
number be x.
[tex] \\ [/tex]
Part 1 :-
Statement :-
21 is subtracted from the square of a number.
x² ← square of number
Equation :-
x² - 21
[tex] \\ \\ [/tex]
Part 2 :-
Statement :- the result is 4 times the number.
4 times a number means 4 × x = 4x.
Equation :-
x² - 21 = 4x
[tex] \\ \\ [/tex]
Part 3 :-
So we got our equation i.e x² - 21 = 4x , now we can finally find negetive value of x.
→x² - 21 = 4x
→x² -21 - 4x = 0
→x² - 4x - 21 = 0
→x² + 3x - 7x - 21 = 0
→x(x + 3) - 7x - 21 = 0
→x(x+3) - 7(x + 3) = 0
→(x - 7) (x + 3) = 0
Comparing:-
- x - 7 = 0
- x = 7 ← possitive value
- x + 3 = 0
- x = - 3 ←negetive value
[tex] \\ [/tex]
Required answer :-
[tex]\boxed{\pmb{\sf -3}}[/tex]
