Question

第三周周侧1.下列各式中,相等关系一定成立的是( )A.(x-y)2=(y-x)2 B.(x+6)(x-6)=x2-6C

Answer 1

(1)A(2)B(3)C(4)C(5)A(6)C(7)1-5a 2x+3 -2a2+5b (8)(100-1)(100+1)=9999

(9) [z+(x-y)][z-(x-y)]=z2-(x-y)2 (10) 10 (11) 4ab 1/2 -2ab 2ab

(12) (a+b)2-(a-b)2=a2+2ab+b2-a2+2ab-b2=4ab

(3x-4y)2-(3x+y)2=9x2-24xy+16y2-9x2-6xy-y2=15y2-30xy