1.-(a+3)=2a-15
a=4
(a+3)^2=49
2.2m+2=4^2=16
m=7
3m+n+1=5^2=25
n=3
m+2n=13
3.根号下（2^2+1^2）=根号下5约等于2.2
4.AD^2+DC^2=AC^2
DC=2根号下7
AD^2+AB^2=BD^2
BD=2根号下34
DC^2+BC^2=BD^2
BC约等于12.8
1.已知某数有两个平方根分别是a+3与2a-15,求这个数.
1.-(a+3)=2a-15
a=4
(a+3)^2=49
2.2m+2=4^2=16
m=7
3m+n+1=5^2=25
n=3
m+2n=13
3.根号下（2^2+1^2）=根号下5约等于2.2
4.AD^2+DC^2=AC^2
DC=2根号下7
AD^2+AB^2=BD^2
BD=2根号下34
DC^2+BC^2=BD^2
BC约等于12.8