9514 1404 393
Answer:
z = -7
Explanation:
The equations will be true for all real integers when they are a dependent set. That will be the case when the second equation is a multiple of the first.
Already, we observe that the ratios of x- and y-coefficients are -4:
-12/3 = -4
8/-2 = -4
The equations will be dependent when the constants have that same ratio:
8z/14 = -4 . . . . desired ratio
8z = -56 . . . . . multiply by 14
z = -7 . . . . makes the equations true for all real numbers
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Comment on the question
The system of equations can be made inconsistent (no solutions) or consistent & dependent (infinite solutions) by the choice of z.
However, integer solutions are limited to pairs of the form (2n+2, 3n-4) for integer values of n. The values of x and y are not "all real integers".
Consequently, we have interpreted the question to be asking for the value of z that will make the system of equations have an infinite number of solutions, including both rational and irrational, real and complex values of x and y. They cannot be made to be true for "all real integers" by any choice of z.