已知函数$f\left(x\right)=\frac{1}{2}x-\cos x$，则方程$f\left(x\right)=\frac{\pi }{4}$所有根的和为(    )

若|x+y﹣7|+（3x+y﹣17）²=0，则x﹣2y=____ ．

阅读下面材料，在空白处填入适当的内容（1个单词）或括号内单词的正确形式。

      It is really sad news for Guinness World Records. Tiffany Two, the holder of the  ____(old) cat record, has passed away in hersleep at____ age of 27 years, 2months and 20 days.

        Born on March 13, 1988 in San Diego, California,Tiffany Two ____(buy) by herowner, Sharon Voorhees, from a local pet shop. At that time, the cat was onlysix  ____(week) old. Sharon named her TiffanyTwo in memory of the cat she once____(own) In the 1970s.

        In fact,____ Tiffany Two celebrated her 27^thbirthday back in March, she had lived the equivalent (等量) of 125 human years.

        Despite ____ unbelievable age, Tiffany Two was reported tohave good sight and hearing ____ (recent). Tiffany Two only had minor____ (ill) such as high blood pressure, and Sharondescribed her as “strong and still able to go up and down stairs”.

        “She's not afraid  ____ (play) with anyone or any animal.She walks right past the dogs. She's very active!” Sharon explained.