A quadratic equation with integral coefficients has two different prime numbers as its roots. If the sum of the coefficients of the equation is prime, then the sum of the roots is
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Let the roots of required quadratic equation be α , β ( Where α , β are prime numbers.) So, the equation can be written as
( x − α ) ( x − β ) = x 2 − ( α + β ) + α β
Since the sum of coefficients of the equation is prime:
1 − α − β + α β is prime
( α − 1 ) ( β − 1 ) is prime
The product of two numbers can be prime if and only if one of the numbers is 1
So, α − 1 = 1
α = 2
Now,
( β − 1 ) is prime
also β is prime
So, we're talking about two consecutive prime numbers and fortunately we have just one pair of consecutive prime numbers, i.e., ( 2 , 3 )
β = 3
Therefore, sum of roots of the equation = α + β = 2 + 3 = 5