数学,
急求助啊啊 ,
(1) lim(3x+1)/(2x-5) =lim[3+(1/x)]/[2-(5/x)] =(3+0)/(2-0) =3/2 (2) lim2arctanx/5x =(2/5)limarctanx/x =(2/5)lim[1/(1+x^2)]/1【罗必塔法则】 =(2/5)*[1/(1+0)] =2/5 (3) limln(1+3x)/sin4x =lim[3/(1+3x)]/(4cos4x) =lim3/[4*(1+3x)*cos4x] =3/[4*(1+0)*1] =3/4 (4)y=(1-lnx)/(1+lnx) 则,y'=[(1-lnx)'*(1+lnx)-(1-lnx)*(1+lnx)']/(1+lnx)^2 =[(-1/x)*(1+lnx)-(1-lnx)*(1/x)]/(1+lnx)^2 =[(-1/x)*(1+lnx+1-lnx)]/(1+lnx)^2 =-2/[x*(1+lnx)^2] (5)y=e^x*cosx 则,dy=d(e^x*cosx) =(e^x*cosx-e^x*sinx)dx =e^x*(cox-sinx)dx (6) lim(x^4-16)/(x-2) =lim[(x^2+4)(x^2-4)]/(x-2) =lim[(x^2+4)(x+2)(x-2)]/(x-2) =lim(x^2+4)(x+2) =(2^2+4)(2+2) =32 (7)∫[x^(1/3)-x^(-1/2)]dx =(3/4)x^(4/3)-2x^(1/2)+C (8)∫6x/(1+x^2)dx =3*∫2x/(1+x^2)dx =3*∫[1/(1+x^2)]*d(1+x^2) =3ln(1+x^2)+C (9)∫x^2/(1+x^2)dx =∫[(1+x^2)-1]/(1+x^2)dx =∫[1-1/(1+x^2)]dx =[x-arctanx]| =(1-arctan1)-(0-arctan0) =[1-(π/4)]-(0-0) =1-(π/4) (10)∫x*e^(-x)dx =∫-x*d[e^(-x)] =[-x*e^(-x)]|-∫e^(-x)d(-x) =[-x*e^(-x)]|-[e^(-x)]| =e^(-x)*(-x-1)| =[e^(-1)*(-1-1)]-[e^(-0)*(-0-1)] =(-2/e)+1 =(e-2)/e。
参考附件,最后两题很简单请参考微积分相关例题。
解答完毕
问:t49列车16车厢的79号座位是不是靠窗呢?急急急。。。
答:尾数4和9的座位是靠窗的,而且可以不用管是不是列车长办公席车厢。详情>>
答:详情>>