1.
x2+4x−5ex−1>0
x<−4.252 Domain: (−∞,−4.252)
2.
x+3y−2=0
y=−31x+32 The slope of the tangent line
slope=m=−−311=3
f(x)=x+2x
f′(x)=2x1+2
slope=m=3=2x1+2
2x1=1
x=41
y(41)=41+2(41)=1
The equation of the tangent line in point-slope form is
y−1=3(x−41) The equation of the tangent line in slope-intercept form is
y=3x+41
3.
Domain:(−∞,∞)
f′(x)=(arctan(x2−4x))′=1+(x2−4x)22x−4
f′(x)=0=>1+(x2−4x)22x−4=0
x=2 If x<2,f′(x)<0,f(x) decreases.
If x>2,f′(x)>0,f(x) increases.
The function f is monotone decreasing on (−∞,2).
The function f is monotone increasing on (2,∞).
4.
∫x2(x3+4)2dx
u=x3+4,du=3x2dx
∫x2(x3+4)2dx=31∫u2du=9u3+C
=9(x3+4)3+C 5.
2y+1dy=−tan(x)dx Integrate
∫2y+1dy=−∫tan(x)dx
∫tan(x)dx=∫cos(x)sin(x)dx=−ln∣cos(x)∣+21lnC
21ln∣2y+1∣=ln∣cos(x)∣+21lnC
2y+1=Ccos2(x) Given y(4π)=12
2(12)+1=Ccos2(4π)
C=50The particular solution of the differential equation
2y+1=50cos2(x)
6.
2X+A=3B−AX
A=(−43−32),B=(12−11) Let
X=(x11x21x12x22) Then
2X=(2x112x212x122x22)
AX=(−43−32)(x11x21x12x22)
=(−4x11−3x213x11+2x21−4x12−3x223x12+2x22)
2X+AX=(−2x11−3x213x11+4x21−2x12−3x223x12+4x22)
3B−A=(7301)
(−2x11−3x213x11+4x21−2x12−3x223x12+4x22)=(7301)
−2x11−3x21=73x11+4x21=3
−2x12−3x22=03x12+4x22=1
x21=27−2x11−3x21=7
−x22=23x12+4x22=1
x11=37,x21=−27,x22=−2,x12=3
X=(373−27−2)
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