Solve for n
n\in \left(\frac{-\sqrt{5}-1}{4},\frac{\sqrt{5}-1}{4}\right)
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4n^{2}+2n-1<0
Swap sides so that all variable terms are on the left hand side. This changes the sign direction.
4n^{2}+2n-1=0
To solve the inequality, factor the left hand side. Quadratic polynomial can be factored using the transformation ax^{2}+bx+c=a\left(x-x_{1}\right)\left(x-x_{2}\right), where x_{1} and x_{2} are the solutions of the quadratic equation ax^{2}+bx+c=0.
n=\frac{-2±\sqrt{2^{2}-4\times 4\left(-1\right)}}{2\times 4}
All equations of the form ax^{2}+bx+c=0 can be solved using the quadratic formula: \frac{-b±\sqrt{b^{2}-4ac}}{2a}. Substitute 4 for a, 2 for b, and -1 for c in the quadratic formula.
n=\frac{-2±2\sqrt{5}}{8}
Do the calculations.
n=\frac{\sqrt{5}-1}{4} n=\frac{-\sqrt{5}-1}{4}
Solve the equation n=\frac{-2±2\sqrt{5}}{8} when ± is plus and when ± is minus.
4\left(n-\frac{\sqrt{5}-1}{4}\right)\left(n-\frac{-\sqrt{5}-1}{4}\right)<0
Rewrite the inequality by using the obtained solutions.
n-\frac{\sqrt{5}-1}{4}>0 n-\frac{-\sqrt{5}-1}{4}<0
For the product to be negative, n-\frac{\sqrt{5}-1}{4} and n-\frac{-\sqrt{5}-1}{4} have to be of the opposite signs. Consider the case when n-\frac{\sqrt{5}-1}{4} is positive and n-\frac{-\sqrt{5}-1}{4} is negative.
n\in \emptyset
This is false for any n.
n-\frac{-\sqrt{5}-1}{4}>0 n-\frac{\sqrt{5}-1}{4}<0
Consider the case when n-\frac{-\sqrt{5}-1}{4} is positive and n-\frac{\sqrt{5}-1}{4} is negative.
n\in \left(\frac{-\sqrt{5}-1}{4},\frac{\sqrt{5}-1}{4}\right)
The solution satisfying both inequalities is n\in \left(\frac{-\sqrt{5}-1}{4},\frac{\sqrt{5}-1}{4}\right).
n\in \left(\frac{-\sqrt{5}-1}{4},\frac{\sqrt{5}-1}{4}\right)
The final solution is the union of the obtained solutions.
Examples
Quadratic equation
{ x } ^ { 2 } - 4 x - 5 = 0
Trigonometry
4 \sin \theta \cos \theta = 2 \sin \theta
Linear equation
y = 3x + 4
Arithmetic
699 * 533
Matrix
\left[ \begin{array} { l l } { 2 } & { 3 } \\ { 5 } & { 4 } \end{array} \right] \left[ \begin{array} { l l l } { 2 } & { 0 } & { 3 } \\ { -1 } & { 1 } & { 5 } \end{array} \right]
Simultaneous equation
\left. \begin{cases} { 8x+2y = 46 } \\ { 7x+3y = 47 } \end{cases} \right.
Differentiation
\frac { d } { d x } \frac { ( 3 x ^ { 2 } - 2 ) } { ( x - 5 ) }
Integration
\int _ { 0 } ^ { 1 } x e ^ { - x ^ { 2 } } d x
Limits
\lim _{x \rightarrow-3} \frac{x^{2}-9}{x^{2}+2 x-3}