Question

Sviatoslav solved the quadratic equation x^2-x-1=0 by completing the square. In the process, he came up with the equivalent equation (x+a)^2 = b, where a and b are constants. What is b?

Answer 1

Answer:

$x=\frac{1+\sqrt5}{2}$ and  $x=\frac{1-\sqrt5}{2}$

and b=$\frac{5}{4}$

Step-by-step explanation:

We are given that a quadratic equation

$x^2-x-1=0$

We have to solve the equation by completing square and find the value of b.

$(x)^2-2\times x\times \frac{1}{2}+(\frac{1}{2})^2-(\frac{1}{2})^2-1=0$

$(x-\frac{1}{2})^2-\frac{1}{4}-1=0$

$(x-\frac{1}{2})^2-\frac{1-4}{4}=0$

$(x-\frac{1}{2})-\frac{5}{4}=0$

$(x-\frac{1}{2})^2-(\frac{\sqrt5}{2})^2=0$

$(x-\frac{1}{2})^2=(\frac{\sqrt5}{2})^2$

$x-\frac{1}{2}=\frac{\sqrt5}{2}$ and $x-\frac{1}{2}=-\frac{\sqrt5}{2}$

$x=\frac{\sqrt5}{2}+\frac{1}{2}=\frac{1+\sqrt5}{2}$

And $x=\frac{1}{2}-\frac{\sqrt5}{2}=\frac{1-\sqrt5}{2}$

Therefore,$x=\frac{1+\sqrt5}{2}$ and  $x=\frac{1-\sqrt5}{2}$

and b=$\frac{5}{4}$