Find the positive and negative domains of the following function:
y=(x−21)(x+621)
Determine for which values of x the following is true:
f(x) < 0
Let us solve the problem step by step to find: x values for which f(x) < 0 .
Firstly, identify the roots of the function y=(x−21)(x+621):
- The root from (x−21)=0 is x=21.
- The root from (x+621)=0 is x=−621.
These roots divide the real number line into three intervals:
- x<−621
- −621<x<21
- x>21
To determine where the function is negative, evaluate the sign in each interval:
- For x<−621: Both factors (x−21) and (x+621) are negative, so their product is positive.
- For −621<x<21: (x−21) is negative and (x+621) is positive, thus the product is negative.
- For x>21: Both factors are positive, so their product is positive.
Hence, the function is negative on the interval: −621<x<21.
-6\frac{1}{2} < x < \frac{1}{2}