Posted by Robert on Friday, November 16, 2012 at 12:46pm.
#12 just plug in the numbers
x = (6±√(36+160))/8
= (6±14)/8
= 6/8 + 14/8 or 6/8 - 14/8
= 5/2 or -1
#13
√-16 = √(16 * -1) = √16√-1 = 4i
#14
since i*i = -1, 1/i = -i
(-5+i)/2i = -5/2i + i/2i = 5/2 i + 1/2
or, in standard form, 1/2 + 5/2 i
#15
looking at the 2nd equation, y = x+2, so
x+2 = x^2+5x-3
x^2 + 4x - 5 = 0
(x+5)(x-1) = 0
x = -5 or 1
so, y = -3 or 3
the solutions are thus (-5,-3)(1,3)
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