<h3>
Answer: x = -5, -4, 4 and 5.</h3><h3>All four zeros are real solutions.</h3>
Step-by-step explanation:
Given the polynomial equation  .
.
Adding 400 on both sides to get rid 400 from right side and set 0 on right side, we get 
 .
.
 .
.
Factoring by product sum rule.
We need product of 400 and sum upto -41.
We can see that 400 = -25 × -16 = 400 and -25-16 = -41.
Therefore, 

Making it into two groups, we get 

Factoring out GCF of each group, we get 


Factoring out   and
 and  separately by difference of the squares identity
 separately by difference of the squares identity  , we get
, we get 
 and
 and 
 .
.
Therefore, 

Applying zero product rule,
x-5=0 
x+5=0
x-4=0 and 
x+4=0.
Therefore, 
<h3>x = -5, -4, 4 and 5.</h3><h3>All four zeros are real solutions.</h3>