Đáp án: A: $V_{SABM}=\dfrac{V}{2}$
Giải thích các bước giải:
Ta có: $V=V_{SABCD}=\dfrac{1}{3}d_{(S,(ABC))}.S_{ABCD}$
$V_{SABM}=\dfrac{1}{3}d_{(S,(ABM))}.S_{ABM}$
$\Rightarrow \dfrac{V}{V_{SABM}}=\dfrac{S_{ABCD}}{S_{ABM}}$
Mà $S_{ABCD}=h.AB$ $(h=d_{(D,AB)}=d_{(M,AB)})$
$S_{ABM}=\dfrac{1}{2}h.AB$
$\Rightarrow \dfrac{V}{V_{SABM}}=\dfrac{1}{\dfrac{1}{2}}=2$
$\Rightarrow V_{SABM}=\dfrac{V}{2}$