Solve x^2+4x-5<0

$$x ^ { 2 } + 4 x - 5 < 0$$

Solve for x

$$x\in \left(-5,1\right)$$

Steps Using the Quadratic Formula

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.

$$x^{2}+4x-5=0$$

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 1 for a, 4 for b, and -5 for c in the quadratic formula.

$$x=\frac{-4±\sqrt{4^{2}-4\times 1\left(-5\right)}}{2}$$

Do the calculations.

$$x=\frac{-4±6}{2}$$

Solve the equation x=\frac{-4±6}{2} when ± is plus and when ± is minus.

$$x=1 x=-5$$

Rewrite the inequality by using the obtained solutions.

$$\left(x-1\right)\left(x+5\right)<0$$

For the product to be negative, x-1 and x+5 have to be of the opposite signs. Consider the case when x-1 is positive and x+5 is negative.

$$x-1>0 x+5<0$$

This is false for any x.

$$x\in \emptyset$$

Consider the case when x+5 is positive and x-1 is negative.

$$x+5>0 x-1<0$$

The solution satisfying both inequalities is x\in \left(-5,1\right).

$$x\in \left(-5,1\right)$$

The final solution is the union of the obtained solutions.

$$x\in \left(-5,1\right)$$