I think he is not correct because there is negative number so it can't be greater than one
Answer:
7a-12
Step-by-step explanation:
explanation is in the pic.
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Given:
y is directly proportional to x.
when 
To find:
The equation that connects y with x.
Solution:
It is given that, y is directly proportional to x. So,

...(i)
Where, k is the constant of proportionality.
We have,
when
. Substituting these values in (i), we get
Divide both sides by 5.
Substituting
in (i), we get
Therefore, the required equation is
.
Answer:
Step-by-step explanation:
The zero of a function is also known as the x-intercept of a function. The x-intercept of a function exists where y = 0. So we will begin by setting each of those lines = 0:
4x - 20 = 0 and -1/2x + k = 0 and then solve each for x:
4x = 20 so
x = 5 and
-1/2x = -k and
1/2x = k so
x = 2k. Now we set the 2 x expressions equal to each other and solve for k:
5 = 2k so
k = 5/2