mathematics

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1. If $ is defined for all positive numbers x and y by x$y = 3x + 8y - y^3, then 10$2 =
A. 38
B. 102
C. 14
D. 20

2. If & is defined for all positive numbers w and z by w & z = 15wz - 10w + 2 then 3 & 4 =
A. 67
B. 77
C. 142
D. 152

3. All of the following are in the domain of f(x) = 5/ x + 2 except:
A. 5
B. -5
C. 2
D. -2

could you explain to me how to get the answer for them

  • mathematics -

    1 and 2

    the operations are defined, so just sub in as defined.

    1.
    10$2 = 3(10) + 8(2) - 2^3 = ....

    same for #2

    3. f(x) = 5/x + 2
    the function is defined for all real values of x, except x = 0
    This is not one of your choices, so the question is bogus.

    If you meant f(x) = 5/(x+2) , then the function is defined for all real values of x, except x = -2

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