His parents didn't earn much money so he dropped out of school because of p____(贫穷).
下列多项式应提取公因式5a2b的是( )
已知线段d是线段a、b、c的第四比例项,其中a=2cm,b=4cm,c=5cm,则d等于( ).
7∶28=15∶x
x=____