《2025年快乐过暑假江苏凤凰科学技术出版社八年级提优版》

6. 若方程$x^{2}-2ax+3= 0$有一个根是1,则a的值是 2。

答案： 2

7. 小明在解方程$x^{2}-5x= -3$的过程中出现了错误,其解答如下:
解:$\because a= 1,b= -5,c= -3$,………第一步
$\therefore b^{2}-4ac= (-5)^{2}-4×1×(-3)= 37$,………第二步
$\therefore x= \frac {5\pm \sqrt {37}}{2}$,………第三步
$\therefore x_{1}= \frac {5+\sqrt {37}}{2},x_{2}= \frac {5-\sqrt {37}}{2}$。………第四步
(1)问:小明的解答是从第一步开始出错的。
(2)请写出本题正确的解答。
将方程$x^{2}-5x = -3$移项化为一般形式$x^{2}-5x + 3 = 0$，其中$a = 1$，$b = -5$，$c = 3$。$\Delta = (-5)^{2}-4×1×3 = 25 - 12 = 13$，$x = \frac{5\pm\sqrt{13}}{2}$，所以$x_{1} = \frac{5 + \sqrt{13}}{2}$，$x_{2} = \frac{5 - \sqrt{13}}{2}$。

答案：
(1)一；
(2)将方程$x^{2}-5x = -3$移项化为一般形式$x^{2}-5x + 3 = 0$，其中$a = 1$，$b = -5$，$c = 3$。$\Delta = (-5)^{2}-4×1×3 = 25 - 12 = 13$，$x = \frac{5\pm\sqrt{13}}{2}$，所以$x_{1} = \frac{5 + \sqrt{13}}{2}$，$x_{2} = \frac{5 - \sqrt{13}}{2}$。

一 选用方框内的单词或词组填空,其中有一个单词或词组是多余选项
modest energetic organized creative grammer curious about
1. Mr White is so creative and makes so many nice model cars for his son.
2. Students from other countries are curious about Chinese history.
3. My grandfather is as energetic as a young man and hates sitting there doing nothing.
4. Jack is a top student in our class but he is very modest.
5. Ms Green is a(n) organized person. She always plans everything well.

答案： 1. creative 2. curious about 3. energetic 4. modest 5. organized

二 完形填空
The kitchen is not just where we prepare meals. In many places, the kitchen is the heart of the home. It is where we 1(C) our day with a cup of coffee or tea. It's where we connect with our family and friends. We talk about our days while we make dinner or have something to eat. The kitchen is where we 2(D) ourselves, body and soul. So, it can be a very busy room in the house.
Sometimes you need order in the kitchen for things to run 3(C). Sometimes you need one person to be in charge. 4(A) you are cooking dinner for your friends. As you are making the soup, your friend Sara 5(A) it and says, "This needs more salt. " So, she adds more salt.
Then Harlan comes in. He tastes your 6(B) and says, "You didn't put enough pepper. " So, he grinds(磨碎) some fresh black pepper into the pot.
Cecilia sees him. She tastes the soup and says, "You forgot vinegar. It's my 7(C) ingredient. " Then she 8(A) in some vinegar.
You are happy to 9(B) time with your friends. But, quite frankly, all their opinions about your soup are becoming 10(C). Worst of all, you taste the soup and it's 11(B)!
And that is where we get the expression "Too many cooks 12(A) the soup". This expression describes an age-old 13(D): if too many people help complete a task, it may not go very well.
So there should be a cook in the kitchen. He is the 14(A). Other people can be assistants helping him. And the cook has the final 15(D).
1. A. enjoy B. finish C. start D. spend
2. A. prepare B. eat C. cook D. feed
3. A. frequently B. actively C. smoothly D. quickly
4. A. Imagine B. Prove C. Probably D. Dream
5. A. tastes B. heats C. mixes D. drinks
6. A. meat B. soup C. vegetable D. food
7. A. wonderful B. famous C. secret D. delicious
8. A. pours B. fills C. takes D. blows
9. A. take B. spend C. need D. use
10. A. charming B. inviting C. annoying D. useful
11. A. salty B. awful C. sour D. hot
12. A. spoil B. share C. make D. drink
13. A. mystery B. discovery C. tradition D. problem
14. A. leader B. host C. friend D. manager
15. A. method B. direction C. advice D. say

答案： 1. C 2. D 3. C 4. A 5. A 6. B 7. C 8. A 9. B 10. C 11. B 12. A 13. D 14. A 15. D