Solve the equation 2x-15+x^2=0

x^2+2x-15=0

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Answer

$x_1=3,\:x_2=-5$

Step by step solution

Problem

$x^2+2x-15=0$
1

To find the roots of a polynomial of the form $ax^2+bx+c$ we use the quadratic formula, where $a=1$, $b=2$ and $c=-15$

$x =\frac{-b\pm\sqrt{b^2-4ac}}{2a}$
2

Substituting the values of the coefficients of the equation in the quadratic formula

$x=\frac{2\left(-1\right)\pm \sqrt{60+2^2}}{2}$
3

Multiply $-1$ times $2$

$x=\frac{-2\pm \sqrt{60+2^2}}{2}$
4

Calculate the power

$x=\frac{-2\pm \sqrt{60+4}}{2}$
5

Add the values $4$ and $60$

$x=\frac{-2\pm \sqrt{64}}{2}$
6

Calculate the power

$x=\frac{-2\pm 8}{2}$
7

To obtain the two solutions, divide the equation in two equations, one when $\pm$ is positive ($+$), and another when $\pm$ is negative ($-$)

$x_1=\frac{-2+ 8}{2}\:\:,\:\:x_2=\frac{-2- 8}{2}$
8

Simplifying

$x_1=3,\:x_2=-5$
9

We found that the two real solutions of the equation are

$x_1=3,\:x_2=-5$

Answer

$x_1=3,\:x_2=-5$

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Problem Analysis

Main topic:

Quadratic formula

Time to solve it:

0.21 seconds

Views:

158