【单选题】已知x1(t)*x2(t)=y(t),则X1(t-t1)*x2(t-t2)等于 A. y（t） B. y(t-t1) C. y(t-t1-t2) D. y(t1-t2)

曲线方程x=1-t2,y=t-t2,它在t=1处的法线方程为

Fill in the blankFor the expressionf(t)=tε(t)+2ε(t−2)−tε(t−2),f(3)=______ .

已知向量组\(\alpha_{1}=(1,1,2)^T,\alpha_{2}=(3,t,1)^T,\alpha_{3}=(0,2,-t)^T,\)线性相关\(，\)则\(t\)=\(（ \quad ）\)。 A: 、\(t=5\)或\(t=-2\) B: 、\(t=5\)或\(t=2\) C: 、\(t=-5\)或\(t=2\) D: 、\(t=1\)或\(t=-2\)

设\(z = {e^{x - 2y}}\)，而\(x = \sin t\)，\(y = {t^3}\)，则全导数\( { { dz} \over {dt}} = \) A: \({e^{\sin t - {t^3}}}(\cos t - 6{t^2})\) B: \({e^{\sin t - 2{t^3}}}(\sin t - 6{t^2})\) C: \({e^{\cos t - 2{t^3}}}(\cos t - 6{t^2})\) D: \({e^{\sin t - 2{t^3}}}(\cos t - 6{t^2})\)

求微分方程[img=269x55]17da6536a9fba07.png[/img]的通解； （ ） A: (C15*sin(2*t))/exp(3*t) + (C16*sin(2*t))/exp(3*t) B: (C15*cos(2*t))/exp(3*t) - (C16*sin(2*t))/exp(3*t) C: (C15*cos(2*t))/exp(3*t) + (C16*cos(2*t))/exp(3*t) D: (C15*cos(2*t))/exp(3*t) + (C16*sin(2*t))/exp(3*t)

一阶常微分方程[img=152x26]1802e4d6075ee4f.png[/img]的通解为 A: sin(2*t)/5-cos(2*t)/10+C*exp(-4*t) B: sin(2*t)/7+cos(2*t)/5-C*exp(-3*t) C: sin(2*t)/7-C*cos(2*t)/10+C*exp(-2*t) D: sin(2*t)/7-cos(2*t)/7+C*exp(-5*t)

【多选题】若f 1 (t) = ɛ (-t) , f 2 (t) = e t ,则f 1 (t)* f 2 (t) = A. f 1 ꞌ (t)* f 2 (–1) (t) B. f 1 (–1) (t)* f 2 ꞌ (t) C. f 1 (t-3)* f 2 (t+3) D. f 1 (–3) (t)* f 2 ꞌꞌꞌ (t)

设\(z = {e^{x - 2y}}\)，而\(x = \sin t,\;y = {t^3},\)则\( { { dz} \over {dt}} = \)( ) A: \({e^{\sin t - 2{t^3}}}\) B: \({e^{\sin t - 2{t^3}}}\left( {\cos t - 6{t^2}} \right)\) C: \({e^{\sin t - 2{t^3}}}\ {\sin t } \) D: \({e^{\sin t - 2{t^3}}}\,{t^3}\)

向量组α1=(1，1，2)T，α2=(3，t，1)T，α3=(0，2，-t)T线性无关的充分必要条件是______． A: t=5或t=-2 B: t≠5且t≠-2 C: t≠-5或t≠-2 D: A，B，C均不正确