Câu 24 : hình D

Câu 25 : hình A

Câu 26 : hình C

24.

\(\left\{{}\begin{matrix}SA\perp\left(ABCD\right)\Rightarrow SA\perp BC\\AB\perp BC\left(gt\right)\end{matrix}\right.\) \(\Rightarrow BC\perp\left(SAB\right)\)

25.

Gọi O là tâm đáy \(\Rightarrow SO\perp\left(ABC\right)\Rightarrow\widehat{SAO}\) là góc giữa SA và (ABC)

\(AO=\dfrac{2}{3}.\dfrac{1.\sqrt{3}}{2}=\dfrac{\sqrt{3}}{2}\)

\(\Rightarrow cos\widehat{SAO}=\dfrac{AO}{SA}=\dfrac{1}{2}\Rightarrow\widehat{SAO}=60^0\)

26.

\(dy=y'dx=\left(x^2\right)'dx=2xdx\)

Câu 27:

\(C_3H_4+AgNO_3+NH_3\rightarrow C_3H_3Ag+NH_4NO_3\\ C_2H_2+2AgNO_3+2NH_3\rightarrow Ag_2C_2+2NH_4NO_3\\ n_{C_3H_4}=\dfrac{1,8}{40}=0,045\left(mol\right);n_{C_2H_2}=\dfrac{0,52}{26}=0,02\left(mol\right)\\ n_{C_3H_3Ag}=n_{C_3H_4}=0,045\left(mol\right)\\ n_{Ag_2C_2}=n_{C_2H_2}=0,02\left(mol\right)\\ m_{kt}=m_{C_3H_3Ag}+m_{Ag_2C_2}=0,045.147+240.0,02=11,415\left(g\right)\\ Chọn.B\)

\(n_{Br_2}=\dfrac{32}{160}=0,2\left(mol\right)\\ Đặt:n_{C_3H_6}=a\left(mol\right);n_{C_3H_4}=b\left(mol\right)\\ PTHH:C_3H_6+Br_2\rightarrow C_3H_6Br_2\\ C_3H_4+2Br_2\rightarrow C_3H_4Br_4\\ \Rightarrow\left\{{}\begin{matrix}42a+40b=6,2\\a+2b=0,2\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}a=0,1\\b=0,05\end{matrix}\right.\\ \Rightarrow\%m_{C_3H_6}=\dfrac{0,1.42}{6,2}.100\approx67,74\%\\ Chọn.A\)

\(n_{Br_2}=\dfrac{0,8}{160}=0,005\left(mol\right)\\ C_2H_4\left(dư\right)+Br_2\rightarrow C_2H_4Br_2\\ n_{C_2H_4\left(dư\right)}=n_{Br_2}=0,005\left(mol\right)\\ n_{C_2H_4\left(đã.p.ứ.với.H_2\right)}=\dfrac{2,24}{22,4}-0,005=0,095\left(mol\right)\\ C_2H_4+H_2\rightarrow\left(Ni,t^o\right)C_2H_6\\ Vì:\dfrac{0,095}{1}< \dfrac{3,36:22,4}{1}\Rightarrow C_2H_4hết,H_2dư\\ H=\dfrac{0,095}{0,1}.100\%=95\%\\ Chọn.C\)

125.(-26)+26.(-25)

= -125.26+26.(-25)

= [-125+(-25)].26

= -150.26

= -3900

\(125.\left(-26\right)+26.\left(-25\right)\)

\(=\left(-125\right).26+26.\left(-25\right)\)

\(=26.\left[\left(-125\right)+\left(-25\right)\right]\)

\(=26.\left(-150\right)\)

\(=-3900\)

\(125.\left(-26\right)+26.\left(-25\right)\)

\(=\left(-125\right).26+26.\left(-25\right)\)

\(=26.\left(-125\right)+\left(-25\right)\)

\(=26.\left(-150\right)\)

\(=-3900\)

:D

a)-250

b)150

c)-60

d)-202

e)-390

cần làm ra cụ thể ko

a)\(\text{ (-34) + (-91) + (-26) + (-99)}\\ =\left[\left(-34\right)+(-26)\right]+\left[(-91)+(-99)\right]\\ =-60+\left(-190\right)\\ =-250\)