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45; 41; =-22; 2c+3d 4c-5d' a Bài 2. Cho n=- - Chứng minh: b 1) (a+c)(b¬d)=(a-c)(b+d); 2) (a + c)b = (b+d)a; 3) a (b-d)=b(a-c); 4) (b+d)c=(a+c)d; 5) (b-d)c=(a-c)d; (a+b)(c-d)=(a-b)(c+d); (2b-3d)=(2a-3c)(2b+3d); 6) 7) (2a+3c) 8) (4a+3b) (4c-3d) = (4a-3b)(4c+3d); 9) (2a+3b) (4c-5d) = (4a- ...