某种商品进货单价为40元，按单价每个50元售出，能卖出50个．如果_爱下问搜题

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问题解答题

某种商品进货单价为40元，按单价每个50元售出，能卖出50个．如果零售价在50元基础上每上涨1元，其销售量就减少一个，问零售价上涨到多少元时？销售这批货物能取得最大利润？最大利润是多少元？

答案

设售价上涨x元，获得的利润y元，

由题意知y=（50+x-40）•（50-x）

=-（x-20）²+900，（0＜x＜50，x∈N^*）

当x=20时，y_max=900元；

多项选择题

整流站基本控制配置（）。

A.最小触发角控制

B.直流电流控制

C.直流电压控制

D.低压限流控制

完形填空

It was silent in Mom’s hospital room. Only the sound of her heart monitor interrupted the     moments of what seemed to be a peaceful sleep. It had been several hours since her operation. I wanted her to wake up. I needed to     to her. Last night, I shouted at her because she had allowed my     sister to visit her when she had     our mom for years.
“Shame on you!” she had said firmly. “Moms don’t stop     their children just because one of them chose to leave her. A mother always loves more than she’s loved     .”
I thought, “Shame on you! When I do something wrong or when a friend is     to her, that’s all she will ever say. How about standing up for you     for once, Mom?”
My mom’s groaning（呻吟）broke my     . she couldn’t speak,     her eyes were moving, looking for something. She     her notebook and pen next to her bed. I gently handed them to her. She     slowly, and then turned the notebook around for me to read.
“I forgive you,” it     .
Tears ran down my face. I felt     . As I began to speak, I was     by the loud arguing of two seemingly angry nurses on the opposite side of the room. My mom suddenly began writing on her notebook, and then stopped to      the piece of paper. She handed it to me, signaling me to give it to the nurses. They read it, looked      at my mom and quietly left the room.
“What did you write, Mom?” I asked.
She smiled sweetly but said nothing.     , I knew what she had written on that piece of paper. How     those three little words are!
I kissed my mom goodbye and     to find my sister.

D．concentration

C．looked through

D．reached for

D．interrupted