SOLUTION: Find the number of positive integers n, {{{1<=n<=1000}}}, for which the polynomial {{{x^2 + x - n}}} can be factored as the product of two linear factors with integer coefficients.
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Polynomials-and-rational-expressions
-> SOLUTION: Find the number of positive integers n, {{{1<=n<=1000}}}, for which the polynomial {{{x^2 + x - n}}} can be factored as the product of two linear factors with integer coefficients.
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Question 1157075: Find the number of positive integers n, , for which the polynomial can be factored as the product of two linear factors with integer coefficients. Answer by ikleyn(52810) (Show Source):
The polynomial of this kind is factorable IF and ONLY IF " n " is the product of two consecutive integer numbers n = m*(m+1).
Then x^2 + x -n = (x+m)*(x-(m+1)).
So, you should determine the number of all such positive n's under the condition 1 <= m*(m+1) <= 1000.
Notice that " m " can be positive and negative, as well.
So, you need to find the number of solutions to this compound inequality
1 <= m*(m+1) <= 1000.
The solutions are -32 <= m <= 31; but you should reject negative m's and m = 0.
So, the number of such positive n's is 31.