Answer:
Step-by-step explanation:
Let the number be x
by given condition,
4x = (x)² - 21
4x = x²- 21
0 = x² - 4x - 21
0 = x² - 7x + 3x - 21
0 = x ( x-7) + 3 ( x - 7)
0 = (x+3)(x-7)
hence
x + 3 =0.....
x = -3---------1
x - 7 = 0
x = 7 ------------2
we got value of x from 1 and 2.. but the question says positive value of x.
hence, x = 7 is the required value of x.
