Hydroponics ______ the cultivation of plants without soil.A.doesB.isC.doD.are
Hydroponics ______ the cultivation of plants without soil.
A.does
B.is
C.do
D.are
Hydroponics ______ the cultivation of plants without soil.
A.does
B.is
C.do
D.are
证明下列各式. (1)f1(t)*f2(t)=f2(t)*f1(t); (2)f1(t)*[f2(t)*f3(t)]=f3(t)*[f1(t)*f2(t)]; (3)a[f1(t)*f2(t)]=[af1(t)]*f2(t)=f1(t)*[af2(t)](a为常数); (4)eat[f1(t)*f2(t)]=[eatf1(t)]*[eatf2(t)](a为常数); (5)[f1(t)+f2(t)]*[g1(t)+g2(t)]=f1(t)*g1(f)+f2(t)*g1(t)+f1(t)*g2(t)+f2(t)*g2(t);
(7)f(t)*δ(t)=f(t); (8)f(t)*δ(t—t0)=f(t—t0); (9)f(t)*δ’(t)=f’(t);
A.IComparer<T>
B.IEnumerable<T>
C.IEnumerator<T>
D.IEqualityComparer<T>
下列等式不成立的是___________。
A.f1(t一t0)*f2(t+t0)=f1(t)*f2(t)
B.
C.f(t)*δ"(t)=f"(t)
D.f(t)*δ(t)=f(t)
A.y’(t)/x(t)
B.-y’(t)/x(t)
C.y’(t)/x’(t)
D.y(t)/x’(t)
E.-y(t)/x’(t)
A.mustn’t
B.shouldn’t
C.wouldn’t
D.mightn’t