How do you solve the quadratic using the quadratic formula given $x^{2} - 4 x - 7 = 0$ $x^2-4x-7=0$ ?

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Answer 1 · 2017-08-09T13:08:28

$x = 5.31662479 \lor x = - 1.31662479$ $x=5.31662479vvx=-1.31662479$

$x^{2} - 4 x - 7 = 0$ $x^2-4x-7=0$
First you calculate the discriminant.

$D = {(- 4)}^{2} - 4 \cdot 1 \cdot - 7 = 16 + 28 = 44$ $D=(-4)^2 -4*1*-7=16+28=44$ ( $D = b^{2} - 4 \cdot a \cdot c$ $D=b^2-4*a*c$ )

Then you use the general formula $x = \frac{- b \pm \sqrt{D}}{2 a}$ $x=(-b+-sqrtD)/(2a)$

Which gives: $x = \frac{4 \pm \sqrt{44}}{2 \cdot 1} = x = 5.31662479 \lor x = - 1.31662479$ $x= (4+- sqrt44)/(2*1)= x=5.31662479vvx=-1.31662479$

How do you solve the quadratic using the quadratic formula given x2−4x−7=0x^2-4x-7=0?