The value of k is
Given:
x-y=k.............(eq i)
2x²+y²-15..............(eq ii)
We would make y the subject formula in eq ii
2x²+y²-15= 0
2x² + y²= 15
y²= 15-2x²
y= ...........(eq iii)
Substitute the value of y into eq i
x-(= k
x- (= k
k=
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Answer:
The third option (9+-
-
)
Step-by-step explanation:
With FOIL, this can be expanded. (a+b)(a-b) is equal to a²+ab-ab-b² or a²-b².
In this case, all the answers have 4 terms, so we want the first option. This makes the equation 3²+(3×)-(3×
)-(
)².
Solving these gives 9+-
-7. This is the same as 9+
-
-
.
**This content involves multiplying with surds and expanding perfect squares, which you may wish to revise. I'm always happy to help!
