If $f(x) = 2x^2 - 3x + 5$, find the value of x when $f(x)$ equals 12.
Answer 1
Given the function $f(x) = 2x^2 – 3x + 5$, we need to find the value of $x$ when $f(x) = 12$.
We start by setting $f(x) = 12$:
$$ 2x^2 – 3x + 5 = 12 $$
Next, we simplify the equation by subtracting 12 from both sides:
$$ 2x^2 – 3x – 7 = 0 $$
Now, we solve this quadratic equation using the quadratic formula:
$$ x = \frac{-b \pm \sqrt{b^2 – 4ac}}{2a} $$
For the equation $2x^2 – 3x – 7 = 0$, we have $a = 2$, $b = -3$, and $c = -7$. Substituting these values into the quadratic formula:
$$ x = \frac{-(-3) \pm \sqrt{(-3)^2 – 4 \cdot 2 \cdot (-7)}}{2 \cdot 2} $$
$$ x = \frac{3 \pm \sqrt{9 + 56}}{4} $$
$$ x = \frac{3 \pm \sqrt{65}}{4} $$
Thus, the two possible solutions are:
$$ x = \frac{3 + \sqrt{65}}{4} $$
or
$$ x = \frac{3 – \sqrt{65}}{4} $$
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