For the real numbers \(m\) \(=\) 26 and \(n\) \(=\) 57, if \(m\) is increased by \(u\) \(=\) \(2\) and \(n\) is decreased by \(v\) \(=\) \(6\), then show that the  increment in product is always equal to \(un\) \(-\) \(mv\) \(-\) \(uv\).
 
Proof:
 
Given, \(m\) \(=\) 26, \(n\) \(=\) 57, \(u\) \(=\) \(2\), and \(v\) \(=\) \(6\).
 
Their product \(mn\) \(=\) .
 
By the given condition, the new product is given by .
 
The value of the new product \(=\)
 
The difference in products \(=\)
 
By the distributive property, the increment in product is given by .
 
The increment in product using the obtained property \(=\) .
 
Difference in product  Increment in product
 
Hence, proved.