Umm.. I have to see the problems, we might not have the same textbooks so
The value of k is 8 hope i was helpful
Answer: 
Step-by-step explanation:
To find the solutions of the quadratic equation given in the problem, you can apply the proccedure shown below:
- Subtract 40 from both sides of the equation.
- Multiply both sides of the equation by -1
- Apply square root to both sides of the equation.
Therefore, by applyin the steps above, you obtain:

Answer: The value of x =2 units.
Explanation:
Since we have given that
AD= CD
BE= EA
So, we get that D and E are the mid-points of AC and AB respectively.
So, by Mid- point theorem , which states that the line joining the two midpoints is parallel to third side and it is half in length of third side i.e.

So, we put the value of DE and BC ,

Hence, the value of x =2 units.