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Solve the quadratic equation [tex]3x^2 + x - 5 = 0[/tex].

Give your answers to 2 decimal places.

Optional working:

Answer:


Sagot :

To solve the quadratic equation \(3x^2 + x - 5 = 0\), we will use the quadratic formula, which is given by:

[tex]\[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \][/tex]

Here, the coefficients \(a\), \(b\), and \(c\) are:
\(a = 3\), \(b = 1\), and \(c = -5\).

First, we need to calculate the discriminant (\(\Delta\)), which is part of the quadratic formula under the square root. The discriminant is given by:

[tex]\[ \Delta = b^2 - 4ac \][/tex]

Substituting the values of \(a\), \(b\), and \(c\):

[tex]\[ \Delta = (1)^2 - 4(3)(-5) \][/tex]
[tex]\[ \Delta = 1 - (-60) \][/tex]
[tex]\[ \Delta = 1 + 60 \][/tex]
[tex]\[ \Delta = 61 \][/tex]

The discriminant is 61. Since the discriminant is positive, we will have two distinct real roots.

Next, we calculate the roots using the quadratic formula. The two possible solutions are:

[tex]\[ x_1 = \frac{-b + \sqrt{\Delta}}{2a} \quad \text{and} \quad x_2 = \frac{-b - \sqrt{\Delta}}{2a} \][/tex]

Substituting the values of \(a\), \(b\), and \(\Delta\):

[tex]\[ x_1 = \frac{-1 + \sqrt{61}}{6} \][/tex]
[tex]\[ x_2 = \frac{-1 - \sqrt{61}}{6} \][/tex]

To find the approximate values of these roots, we will compute the value inside the square root and then evaluate the expressions:

[tex]\[ \sqrt{61} \approx 7.81 \][/tex]

Now substituting this approximation into the expressions for \(x_1\) and \(x_2\):

[tex]\[ x_1 = \frac{-1 + 7.81}{6} \approx \frac{6.81}{6} \approx 1.14 \][/tex]
[tex]\[ x_2 = \frac{-1 - 7.81}{6} \approx \frac{-8.81}{6} \approx -1.47 \][/tex]

Thus, the solutions to the quadratic equation \(3x^2 + x - 5 = 0\) are approximately:

[tex]\[ x_1 \approx 1.14 \quad \text{and} \quad x_2 \approx -1.47 \][/tex]