It is prime only for x = -4 and x = -7. For any other integer x, the value of this expression is not prime.
First of all, a Prime number is a number only divisible by two positive numbers: 1 and itself.
Factoring out the expression, we have:
x² + 11x + 30 = (x+5) (x+6)
So the result is divisible by at least two numbers, (x+5) and (x+6). The only cases where this lead to a prime number are the ones where one of the factors is 1 and the other isn't 0 (since 0 is not prime):
x = -4 => (-4 + 5) (-4 + 6) = 2
x = -7 => (-7 + 5) (-7 + 6) = (-2) (-1) = 2
If x must be a counting number, then there's no x for which the expression value is prime.
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x2 + 11x + 30 = 0 (x + 5)(x + 6) = 0 so the roots are -5 and -6
The factors of (x2 + 11x + 30) are (X + 5) and (x + 6)You want to look for two numbers, when multiplied equal 30, and when added equal 11. Start with factors of 30, and see what they add to: 5+6=11, and 5*6=30.
The actual equation itself is the polynomial. There is no polynomial for it, and your question doesn't really make sense.
It is: x^2 +11x +24 = (x+8)(x+3) when factored
-x2 - 11x + 26 = -(x2 + 11x - 26) = -(x2 - 2x + 13x - 26) = -[ x(x - 2) + 13(x - 2) ] = -(x + 13)(x - 2) = (x + 13)(2 - x)