16.如图,有甲、乙、丙三种地砖,其中甲、乙是正方形,边长分别为a、b,丙是长方形,长为a,宽为b(其中a>b),如果要用它们拼成若干个边长为(3a+b)的正方形,那么应取甲、乙、丙三种地砖块数的比是( )

| A. | 无法确定 | B. | 2:1:2 | C. | 3:1:2 | D. | 9:1:6 |
15.
如图,当y<0时,自变量x的范围是( )
| A. | x<-2 | B. | x>-2 | C. | x>2 | D. | x<2 |
13.有3张边长为a的正方形纸片,4张边长分别为a、b(b>a)的长方形纸片,5张边长为b的正方形纸片,从其中取出若干张纸片,每种纸片至少取一张,把取出的这些纸片拼成一个正方形(按原纸张进行无空隙、无重叠拼接),则拼成的正方形的边长最长可以为( )
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| A. | a+b | B. | 2a+b | C. | a+2b | D. | 3a+b |