A) ( X-1)(2-X) + (X-3)2 = 4-2X 2X-X2-2+X +X2-6X+9 = 4-2X (0,25 X2) -3X+7 = 4-2X (0,25) X = 3 (0,25) B) (X+1)(X+2)(X-1) – (X-2)3 –X2 = 7X2 -2X+1 X3+2X2-X-2 – ( X3-6X2+12X-8) –X2...
Bài 3: ( 1,5 điểm): Tìm x biết: a) ( x-1)(2-x) + (x-3)
2
= 4-2x 2x-x2
-2+x +x2
-6x+9 = 4-2x (0,25 x2) -3x+7 = 4-2x (0,25) x = 3 (0,25) b) (x+1)(x+2)(x-1) – (x-2)3
–x2
= 7x2
-2x+1 x3
+2x2
-x-2 – ( x3
-6x2
+12x-8) –x2
= 7x2
-2x+1 (0,25) x = 5/11 (0,25)