Question

Which shows the correct substitution of the values a, b, and c from the equation –2 = –x + x2 – 4 into the quadratic formula?

Answer 1

Answer:

We substitute $x=\frac{-(-1)+/-\sqrt{(-1)^2-4(1)(-2)} }{2(1)}$

And simplify $x=\frac{1+/-\sqrt{1-4(1)(-2)} }{2}$

Step-by-step explanation:

First we rearrange the equation -2=-x+x2-4 into standard form of a quadratic $ax^2+bx+c=0$. This equation becomes $x^2-x-2=0$ where a=1, b=-1, and c=-2.

The formula is:

$x=\frac{-b+/-\sqrt{b^2-4ac} }{2a}$.

We substitute $x=\frac{-(-1)+/-\sqrt{(-1)^2-4(1)(-2)} }{2(1)}$

And simplify $x=\frac{1+/-\sqrt{1-4(1)(-2)} }{2}$

$x=\frac{1+/-\sqrt{1+8} }{2}$

$x=\frac{1+/-\sqrt{9} }{2}\\x=\frac{1+/-3 }{2}\\x=2,-1$