Question

数学，求解。（看图）？

别在意语言。第5题，c等于什么？还有第11题。

Answer 1

(1)-4,8,4
(2)(x+1/2)^2+y^2=65/4
(3)设圆方程为(x-a)^2+(y-b)^2=r^2
(5-a)^2+(2-b)^2=r^2
(3-a)^2+(2-b)^2=r^2
2a-b-3=0
a=4,b=2,r=1
(x-4)^2+(y-2)^2=1
(4)设圆方程为(x-a)^2+(y-b)^2=r^2
a-3b=0
a=r或-a=r
a^2-7=(a-b)^2/2
a=3，b=1，r=3
或a=-3，b=-1，r=3
(x-3)^2+(y-1)^2=9或(x+3)^2+(y+1)^2=9

Answer 2

追问

第5的，如果要把a和b同时代替，要怎么代替？

这是答案，但怎么算？

Answer 3

5. 2^a = 5^b = 20^c
alg2 = clg20 , c = alg2/lg20 = alg2/(1+lg2), lg2 = c/(a-c)
同理 c = blg5/lg20 = b(1-lg2)/(1+lg2)
= b[1-c/(a-c)]/[1+c/(a-c)] = b(a-2c)/a
ac = ab - 2bc, c = ab/(a+2b)
11. t = 3^m = 5^n, mlg3=nlg5, lg5 = (m/n)lg3
记 log<t> 45 = x, 则 t^x = 45 = 5*(3^2)
xlgt = lg5+2lg3, xmlg3 = lg5+2lg3 = (m/n + 2)lg3
x = (m/n + 2)/m = (m+2n)/(mn)
,