Answers

2015-08-26T18:39:00+08:00
1. (x^2 +x -6)(x^2 -6x +9)
x^2 x x^2 = x^4
x^2 x -6x = -6x^3
x^2 x +9 = +9x^2
+x x x^2 = -x^3
+x x -6x = -6x^2
+x x +9 = -9x
-6 x +x^2 = -6x^2
-6 x -6x = -36x
-6 x +9 = -54
= x^4 -6x^3 +9x^2 -x^3 -6x^2 -9x -6x^2 -36x -54
= -6x^4 -9x^5 +6x^4 -9x -54

2. (2x^2 -5x +3)(x-3)
+2x^2 x x = +2x^3
-5x x x = -5x^2
+3 x x = +3x
+2x^2 x +3 = +6x^2
-5x x +3 =  -15x
+3 x +3 = +9
= +2x^3 -5x^2 +3x +6x^2 -15x +9
= -10x^5 +18x^3 -15x +9


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