Try this solution:
1. according to the condition

2. for more details see the attached graph.
Answer: [0;+oo)
How about this (see attached image):
Use the four cuts as shown in the image (red lines).
Then assemble 5 equal squares by the numbers: 1 center square and the rest are pieced together using two pieces as shown. All five together add up to the same area as original square because we use all pieces.
The way one gets a hint toward a solution is to see how an area of a square of length 1 can be split into 5 equal square areas:

which indicates we need to find a a triangle with sides 2 and 1 to get the hypotenuse of the right length. That gave rise to the cut pattern (if you look carefully, there are triangles with those side lengths).
Answer: From the figure attached,
Point X is the midpoint of line AC.
Since coordinates of the midpoint of the segment joining endpoints and is given by,
Therefore, coordinates of the point X will be, = (a, a)
From triangle AXB,
Length of AB = 2a
Length of AX =
Length of BX =
=
Length of AX = BX =
Therefore, triangle AXB is an isosceles triangle.
Step-by-step explanation:
The required equation is: 
Option C is correct.
Step-by-step explanation:
The proportional relationship can be found using the equation: 
where x and y are the points and k is the constant of proportionality.
We need to find k.
From the graph given, we can locate points x and y:
x=5, y= 35 then k would be:

x=10, y=70 then k would be:

For each values of x and y, the constant of proportionality k is 7
So, the required equation is: 
Option C is correct.
Keywords: Proportional Relationship
Learn more about Proportional Relationship at:
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Graphing two equations that produces the same line is called Infinite Solutions.