How do you solve $-5x^2 - 8x + 1 = 0$ using the quadratic formula?

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Answer 1 · 2015-08-06T13:12:45

$x_(1,2) = - (4 +- sqrt(21))/5$

For the general form quadratic equation

$color(blue)(ax^2 = bx + c = 0)$

the two solutions can be deterimed by using the quadratic formula

$color(blue)(x_(1,2) = (-b +- sqrt(b^2 - 4ac))/(2a))$

In your case, you have $a=-5$ , $b=-8$ , and $c=1$ . The two solutions will take the form

$x_(1,2) = (-(-8) +- sqrt( (-8)^2 - 4 * (-5) * 1))/(2 * (-5))$

$x_(1,2) = (8 +- sqrt(84))/(-10) = - (4 +- sqrt(21))/5$

This is equivalent to

$x_1 = color(green)(- (4 + sqrt(21))/5)$ and $x_2 = color(green)(- (4 - sqrt(21))/5)$

How do you solve -5x^2 - 8x + 1 = 0-5x^2 - 8x + 1 = 0 using the quadratic formula?