1 Answer

Lars Christoffersen · Answer 1 · 2020-08-27T08:19:24+0000

Answer:

k=4

5x^2-x-4=0

Explanation:

To solve this example we use Viet's rule. So if we have equation:

ax^2+bx+c=0 , then we use Viet :

$x_(1) +x_(2)=(-b)/(a) \\x_(1)*x_(2)=(c)/(a)$

Now, by question we have this :

$x_(1)+x_(2)=(1)/(5)=0.2\\ x_(1)*x_(2)=-(k)/(5) \\\\x_(1)-x_(2)=1.8$

From the last we have :

$x_(1)=1.8+x_(2) \\$

Now use first equation :

$1.8+x_(2)+x_(2)=0,2\\x_(2)=-0.8$

Now, we can find x1=1

Now, we can find k :

$1*(-0.8)=-(k)/(5) \\k=4$

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