Share
When 4 times a positive number is subtracted from the square of the number, the result is 5. Find the number.
Question
When 4 times a positive number is subtracted from the square of the number, the result is 5. Find the number.
in progress
0
Mathematics
3 years
2021-07-26T11:59:22+00:00
2021-07-26T11:59:22+00:00 1 Answers
21 views
0
Answers ( )
Answer:
5
Step-by-step explanation:
x² – 4x = 5
x² – 4x – 5 = 0
the solution of a quadratic equation is
x = (-b ± sqrt(b² – 4ac))/(2a)
a = 1
b = -4
c = -5
x = (4 ± sqrt(16 + 20))/2 = (4 ± sqrt(36))/2
x1 = (4 + 6)/2 = 5
x2 = (4 – 6)/2 = -1
since we are looking only for a positive number, x=5 is the answer.