[tex] {x}^{2} + 4x - 7 = 0 \\ → {x}^{2} + 4x = 7[/tex]
Add the square of the half of the coefficient of the unknown(x) to both sides of the equation.
[tex] {x}^{2} + 4x + ( \frac{4}{2} {)}^{2} = 7 + ( \frac{4}{2} {)}^{2}[/tex]
[tex] {x}^{2} + 4x + (2 {)}^{2} = 7 + (2 {)}^{2} [/tex]
[tex] {x}^{2} + 4x + (2 {)}^{2} = 7 + 4[/tex]
Bring out x and 2 and square them as shown below:
[tex](x + 2 {)}^{2} = 11[/tex]
Now, square root both sides of the equation to find the value of x as shown below:
[tex] \sqrt{(x + 2 {)}^{2} } = \sqrt{11} [/tex]
Add a + or - sign since it is a quadratic equation
[tex]x + 2 = \binom{ + }{ - } \sqrt{11} [/tex]
[tex]x + 2 = \binom{ + }{ - } 3.3166[/tex]
[tex]x = - 2 + 3.166 [/tex] or
[tex]x = - 2 - 3.166[/tex]
Therefore:
[tex]x = 1.17[/tex] or
[tex]x = - 5.17[/tex]
to two decimal places.