A:how much cost they are
B:how much do they cost
C:how much they cost
D:how much are they cost
与椭圆x24+y2=1共焦点且过点Q(2,1)的双曲线方程是( )
将镁粉和碳酸镁的混和物置于氧气中灼烧,直至质量不再改变为止,经测定,灼烧后所得的固体质量与原混和物的质量相同,则原混和物中镁粉和碳酸镁的质量比为
(1)是否有闭区间上连续函数,使得每个函数值恰好取一次?
(2)是否有闭区间上连续函数,使得每个函数恰好取二次?
某炼铁厂,用Fe2O3的质量分数为80%的赤铁矿为原料炼铁,若每天生产含杂质2%的生铁1120t.问需要赤铁矿石多少吨?