Answers

2014-07-18T17:02:45+08:00
If  x -1 is a factor of        x⁴ - 5x² + 4
 then  x =1 must be a zero of the expression
meaning    if you substitute  x =1  in the expression it must equate to   0
thus
             1⁴ - 5 .1² + 4  =   1 -5 + 4 =    0        is equal to  0
therefore x -1 is a factor    x⁴ - 2x² + 4

x⁴ + 3x³ - 4x² + 2x -1          /  substitute   x =  2
16 + 24 - 16 + 4 - 1  =    27
therefore     x -2      is not a factor of  the above expression

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