Question 320464
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Sorry.  Only one question per post.


1.


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ 2x\ +\ 3y\ =\ 40]


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ -2x\ + 2y\ =\ 20]



Add the two equations:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ 2x\ -\ 2x\ +\ 3y\ +\ 2y\ =\ 40\ +\ 20]


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ 0x\ +\ 5y\ =\ 60]


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ y\ =\ 12]


Substitute:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ 2x\ +\ 3(12)\ =\ 40]


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ 2x\ =\ 40\ -\ 36]


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ x\ =\ 2]


John
*[tex \LARGE e^{i\pi} + 1 = 0]
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