Solve this quadratic equation using the quadratic formula x2 plus 8x - 5 equals 0?

Answer 1

Assuming the formula that was meant was x^2 plus 8x minus 5 equals 0 [ x^2 + 8x - 5 = 0 ]

the quadratic formula uses the standard form of a quadratic ax^2 plus bx plus c = 0 [ax^2 + bx + c = 0] comparing this form to the equation we get

a = 1 b = 8 and c = -5

the quadratic formula is:

x = negative b plus or minus the square root of (b^2 minus 4ac) all over 2a

[ x = (-b +- root(b^2 - 4ac))/2a ]

if we substitute in the values we have for a, b and c we get

x = negative 8 plus or minus the square root of (8^2 minus 4*1*(-5)) all over 2*1

[ x = (-8 +- root(8^2 - 4*1*(-5)))/(2*1) ]

simplified we get

x = (-8 +- root(64 + 20))/2

and

x = (-8 +- root(84))/2

and

x = (-8 +- 2*root(21))/2

we get two solutions

x = (-8 - 2*root(21))/2

x approx= (-8.58)

and

x = (-8 + 2*root(21))/2

x approx= (.58)