Assuming 0.4 is in fact, 2 divided by 5 (and not an approximation of some number that would require an infinite amount of decimal places to exactly express), then multiplication by 0.4 is the same as multiplying by 2 and dividing by 5.
This means that multiplying any rational number by 2/5 will yield another rational number (as given x/y as an input, where x and y are integers, and multiplying it by 2/5 giving 2x/5y, will mean that 2x and 5y are also integers, and the result is also rational)
If we multiply an irrational number by 2/5, however, the result will be irrational.
So your answer is any number not in the set of rational numbers, multiplied by 0.4, will yield an irrational number.
It is Associative Property
-4=-1b-(1/3)b
-4=-(4/3)b
-4/-(4/3)=b
b=3
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(1/2)3+(5/3)2
3/6+10/6=13/6
-23/3=13/6a
(-23/3)/(13/6)=a
a=-46/13
The option C) y = 15/x
a) y = 15 x is an example of direct variation, with proportionality constant = 15
b) is an example of linear variation (it is the equation of a straight line that does not pass through the origin)
c) y = 15/x => y*x = 15 = constant which is the characteristic of an inverse relation
d) y = x/15 is an example of an inverse relation, with proportion constant = 1/15
