How do you solve $y = 0.04x+ 8.3x + 4.3$ using the quadratic formula?

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Answer 1 · 2017-11-07T22:50:56

See a solution process below:

Assuming the equation is:

$y = 0.04x^color(red)(2) + 8.3x + 4.3$

For $color(red)(a)x^2 + color(blue)(b)x + color(green)(c) = 0$ , the values of $x$ which are the solutions to the equation are given by:

$x = (-color(blue)(b) +- sqrt(color(blue)(b)^2 - (4color(red)(a)color(green)(c))))/(2 * color(red)(a))$

Substituting:

$color(red)(0.04)$ for $color(red)(a)$

$color(blue)(8.3)$ for $color(blue)(b)$

$color(green)(4.3)$ for $color(green)(c)$ gives:

$x = (-color(blue)(8.3) +- sqrt(color(blue)(8.3)^2 - (4 * color(red)(0.04) * color(green)(4.3))))/(2 * color(red)(0.04))$

$x = (-color(blue)(8.3) +- sqrt(68.89 - 0.688))/0.08$

$x = (-8.3 +- sqrt(68.202))/0.08$

If it is necessary to get to a single number:

$x = (-8.3 - 8.258)/0.08$ and $x = (-8.3 + 8.258)/0.08$

$x = -16.558/0.08$ and $x = -0.042/0.08$

$x = -206.975$ and $x = --0.525$

rounded to the nearest thousandth

How do you solve y = 0.04x+ 8.3x + 4.3y = 0.04x+ 8.3x + 4.3 using the quadratic formula?