Question 219696
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For the first one, use FOIL, First-Outside-Inside-Last


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ (x + 1)(x - 5)]


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


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ x\cdot -5 = -5x]


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ 1\cdot x = x]


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ 1\cdot -5 = -5]


Add up the pieces:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ x^2 -5x + x -5]


Collect like terms:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ x^2-4x-5]


The other two:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ -3x^3-x^2-7]


a. for *[tex \Large x = -1]


Substitute -1 for *[tex \Large x] and do the arithmetic:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ -3(-1)^3-(-1)^2-7]


Since this is an algebra site, I'll let you do your own arithmetic.


b. for *[tex \Large x = 2]


Same thing, different number:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ -3(2)^3-(2)^2-7]


Again, do your own arithmetic.


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