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For an integer $n$, the inequality

\[x^2 + nx + 15 < 0\]has no real solutions in $x$. Find the number of different possible values of $n$.

Respuesta :

Answer:

The number of different possible values are {-7,-6,-5,-4,-3,-2,-1,0,1,2,3,4,5,6,7}.

Step-by-step explanation:

Given : For an integer n, the inequality  [tex]\[x^2 + nx + 15 < 0\][/tex]  has no real solutions in x.

To find : The number of different possible values of n ?

Solution :

The given inequality is   [tex]\[x^2 + nx + 15 < 0\][/tex] have no solution then the discriminant must be less than zero.

i.e. [tex]b^2-4ac<0[/tex]

Here, a=1, b=n and c=15

[tex]{n}^{2} - 4 \times 1 \times 15 \: < \: 0[/tex]

[tex]{n}^{2} - 60 \: < \: 0[/tex]  

[tex]n^2<60[/tex]

[tex]n<\pm \sqrt{60}[/tex]

[tex]n<\pm 7.75[/tex]

i.e. [tex]- 7.75 \: < \: n \: < \: 7.75[/tex]

The integer values are {-7,-6,-5,-4,-3,-2,-1,0,1,2,3,4,5,6,7}.