Answer:
[tex]k=\pm 6[/tex]
Step-by-step explanation:
The given quadratic equation is :
[tex]x^2 - kx + 8 = 0[/tex]
One of the roots of this equation is twice that of the other. Let the roots are [tex]\alpha \ and\ \beta[/tex], [tex]\alpha =2\beta[/tex]
Sum of roots, [tex]\alpha +\beta =\dfrac{-b}{a}[/tex]
[tex]\alpha +\beta =\dfrac{-(-k)}{1}\\\\\alpha +\beta =k\\\\3\beta =k\ .......(1)[/tex]
Product of roots,
[tex]\alpha \beta =\dfrac{c}{a}\\\\2\beta ^2=\dfrac{8}{1}\\\\\beta =\pm 2[/tex]
If [tex]\beta =\pm2[/tex],
[tex]k=3(2)\\\\=\pm 6[/tex]
So, the value of k is equal to [tex]\pm 6[/tex].
