1（a+b-3)(a-b-3)2(x+y+z)^231.234^2+0.766^2+2.468×0.76642010^21（a+b-3)(a-b-3)2(x+y+z)^231.234^2+0.766^2+2.468×0.76642010^2

Question

1 （a+b-3)(a-b-3) 2 (x+y+z)^2 3 1.234^2+0.766^2+2.468×0.766 4 2010^2
1 （a+b-3)(a-b-3)
2 (x+y+z)^2
3 1.234^2+0.766^2+2.468×0.766
4 2010^2

Answer 1

1 （a+b-3)(a-b-3)
= [(a-3)+b][(a-3)-b]
= (a-3)^2-b^2
= a^2-6a+9-b^2
2 (x+y+z)^2
=(x+y)^2+z^2+2(x+y)z
=x^2+y^2+2xy+z^2+2xz+2yz
3 1.234^2+0.766^2+2.468×0.766
=1.234^2+0.766^2+2×1.234×0.766
=(1.234+0.766)^2
=2^2
=4