(x-y)(1/9x-y)-(1/3-y)(1/3+y)
=1/9x^2-xy-1/9xy+y^2-1/9+y^2
=1/9x^2-10/9xy+2y^2-1/9
=1/9(x^2-10xy+18y^2)
(1+1/2)(1+1/2)(1+1/24)(1+1/28)
=1/4(2+1)(2+1)(1+1/24)(1+1/28)
=9/4(1+1/24)(1+1/28)
=9/96(24+1)(1+1/28)
=9/2688 (24+1)(28+1)
=9×25×29÷2688
=2.427
已知√a=√b+1
求(√a+√b)(a+b)(a^2+b^2)(a^4+b^4)
∵√a=√b+1
∴√a-√b=1
a-b=(√a+√b)(√a-√b)=(√a+√b)
(√a+√b)(a+b)(a^2+b^2)(a^4+b^4)
=(a-b)(a+b)(a^2+b^2)(a^4+b^4)
=(a^2-b^2)(a^2+b^2)(a^4+b^4)
=(a^4-b^4)(a^4+b^4)
=a^8-b^8
已知a^2+b^2+4c^2-2a-4b+4c=-6
求a-b+c的值
a^2+b^2+4c^2-2a-4b+4c=-6
a^2+b^2+4c^2-2a-4b+4c+6=0
(a^2-2a+1)+(b^2-4b+4)+(4c^2+4c+1)=0
(a-1)^2+(b-2)^2+(2c+1)^2=0
则 a=1,b=2,c=-0.5
把 a=1,b=2,c=-0.5 代进
a-b+c 得:
a-b+c=1-2-0.5=-1.5