第1个等式：x₁= $\frac{1}{1\times 3}=\frac{1}{2}\left(1-\frac{1}{3}\right)$ ；第2个等式：x₂= $\frac{1}{5\times 3}=\frac{1}{2}\left(\frac{1}{3}-\frac{1}{5}\right)$ ；

第3个等式：x₃= $\frac{1}{5\times 7}=\frac{1}{2}\left(\frac{1}{5}-\frac{1}{7}\right)$ ；第4个等式：x₄= $\frac{1}{9\times 7}=\frac{1}{2}\left(\frac{1}{7}-\frac{1}{9}\right)$ ；

则x_l+x₂+x₃+…+x₁₀=____．

选择正确的句子序号，补全文章。

Building Trust in a Relationship Again

          Trust is a learned behavior that we gain from past experiences.____（1）Trust is a risk.But you can't be successful when there's a lack of trust in a relationship that results from an action where the wrongdoer takes no responsibility to fix the mistake.21·cn·jy·com

          Unfortunately，we've all been victims of betrayal.Whether we've been stolen from，lied to，misled，or cheated on，there are different levels of losing trust.Sometimes people simply can't trust anymore.____ （2）It's understandable，but if you're willing to build trust in a relationship again，we have some steps you can take to get you there.

          ●____（3）Having confidence in yourself will help you make better choices because you can see what the best outcome would be for your well－being.

          ●____（4）If you've been betrayed，you are the victim of your circumstance.But there's a difference between being a victim and living with a “victim mentality”．At some point in all of our lives，we'll have our trust tested or violated.

          ●You didn't lose “everything”．Once trust is lost，what is left？Instead of looking at the situation from this hopeless angle，look at everything you still have and be thankful for all of the good in your life.____（5） Instead，it's a healthy way to work through the experience to allow room for positive growth and forgiveness.

关于天然放射现象，下列说法正确的是（  ）