Question

Solve for x in the equation 3x^2-18x+5=47

Answer 1

$x = 3+- \sqrt{23}$

Answer 2

Answer:

$x$≅$7.80,-1.80$ (rounded to 2 decimal places)

Step-by-step explanation:

This is a quadratic equation : $3x^2-18x+5=47$

Bringing everything to left side:

$3x^2-18x+5=47\\3x^2-18x+5-47=0\\3x^2-18x-42=0$

We can use the quadratic formula to find the value(s) of x:

Quadratic Formula:

• $x=\frac{-b+\sqrt{b^2-4ac} }{2a}$

and

• $x=\frac{-b-\sqrt{b^2-4ac} }{2a}$

Where,

• a is the coefficient of $x^2$
• b is the coefficient of $x$
• c is the constant term

For our question we have:

$a=3\\b=-18\\c=-42$

Plugging in all the values we get:

$x=\frac{-(-18)+\sqrt{(-18)^2-4(3)(-42)} }{2(3)}\\x=\frac{18+\sqrt{828} }{6}$

This is approximately 7.80

and

$x=\frac{-(-18)-\sqrt{(-18)^2-4(3)(-42)} }{2(3)}\\x=\frac{18-\sqrt{828} }{6}$

This is approximately -1.80

So, $x$≅$7.80,-1.80$