Second, choose C. You can understand that if a rectangle has four squares in length and width, the number of squares to be completed from left to right is 2.3. 1.2. In contrast, you can choose C.

3.∠ AOB = 90 and the answer is 135. Maybe point B is mislabeled.

Fourth, choose B, 1 Wrong, X.

Verb (abbreviation of verb) Solution: If the service life is 10 years, after 10 years, the electricity charge for type A refrigerator is1* 0.5 * 365 *10 =1.825 yuan, and that for type B refrigerator is 0.

The price of type A refrigerator is 2 190 yuan, and the price of type B refrigerator is 2190 * (1+10%) = 2,409 yuan, so the price-performance ratio is based on the lowest electricity and refrigerator fees after10 years. Type B refrigerator =1003.75+2409 = 3412.75 yuan, which is lower than the price of type A refrigerator. Therefore, the economic price is = 3412.75-1825 = 1587.75 yuan,158.

Six, choose C, which is 2m.

Seven, choose D, it can be seen from the figure that the length =8-2x and the width =5-2x, then the solution of 2(8-2x)+2(5-2x)≤45-(2*8+2*5) and x≥7/8 is from 8-2x >: 0, 5-2x. 0，x

Eight, choose B. From the equation, we can know that x=5k, y=-2k, and substitute it into the equation to get k=3/2.

9. Solution: If there are X primary school students and Y middle school students in 2005, then X+Y = 5000; In 2006, the number of students increased by 20%x+30%y= 1 160, and x = 3400 and y = 1600 were solved simultaneously, so the borrowing fee was reduced by * * * = 500 * 3400+1.

X. Choose D, x2+y2-2x-6y+10 = (x-1) 2+(y-3) 2 ≥ 0, which is non-negative, that is, take 0 or a positive number.