Answer:
5/V2=2.5×V2
Step-by-step explanation:
This is an isoscelle right triangle:
x²+x²=5²
2x²=5²
x=5/V2=5×V2/2=2.5×V2
where V2=sqrt(2)
Answer:
k = 28
Step-by-step explanation:
12/k = 18/42
Cross multiply.
18k = 12 * 42
18k = 504
Divide both sides by 18.
k = 28
So, this question is basically asking us "If we had an x instead of a 2, would this be true?" We can try and see what we get:

So, if we want to show this we have to change the numerator or denominator in such a way that we can cancel some common factors. Notice that 
If we replace the factored numerator with the original one, we get:

Since we have an equality, this relation is proved.