Chapter 9.4, Problem 5E

To determine

To find the value of c that completes the square.

  $x^2-8x+c$

Answer to Problem 5E

  $c=16$

Explanation of Solution

Given information:

Quadratic equation

  $x^2-8x+c$

Calculation:

Quadratic equation

  $x^2-8x+c\mathrm{............}(1)$

The general form of quadratic equation is $a{x}^2+bx+c$

For making quadratic equation perfect square adding ${\left(\frac{b}{2}\right)}^2$

Here

Adding ${\left(-\frac{8}{2}\right)}^2$ in the equation (1) without c

  $x^2-8x+{\left(-\frac{8}{2}\right)}^2$

Comparing above equation with general quadratic equation

  $c={\left(-\frac{8}{2}\right)}^2$

On solving

  $c=16$

Therefore,

  $x^2-8x+16$ is a perfect square