Question

Tính:

a) \(\int\limits^1_0\left(x^6-4x^3+3x^2\right)dx;\)                b) \(\int\limits^2_1\dfrac{1}{x^4}dx\);                  c) \(\int\limits^4_1\dfrac{1}{x\sqrt{x}}dx\);

d) \(\int\limits^{\dfrac{\pi}{2}}_0\left(4\sin x+3\cos x\right)dx\);              e) \(\int\limits^{\dfrac{\pi}{2}}_{\dfrac{\pi}{4}}\cot^2xdx\);             g) \(\int\limits^{\dfrac{\pi}{4}}_0\tan^2xdx\);

h) \(\int\limits^0_{-1}e^{-x}dx\);                                     i) \(\int\limits^{-1}_{-2}e^{x+2}dx\);                  k) \(\int\limits^1_0\left(3.4^x-5e^{-x}\right)dx\).

Answer 1

a) \(\int\limits_0^1 {({x^6} - 4{x^3} + 3{x^2})dx} = \left. {\left( {\frac{{{x^7}}}{7} - {x^4} + {x^3}} \right)} \right|_0^1 = \frac{1}{7}\)

b) \(\int\limits_1^2 {\frac{1}{{{x^4}}}dx} = \left. {\left( { - \frac{1}{{3{x^3}}}} \right)} \right|_1^2 = \frac{7}{{24}}\)

c) \(\int\limits_1^4 {\frac{1}{{x\sqrt x }}dx} = \left. {\frac{{ - 2}}{{\sqrt x }}} \right|_1^4 = 1\)

d) \(\int\limits_0^{\frac{\pi }{2}} {(4\sin x + 3\cos x)dx} = \left. {\left( { - 4\cos x + 3\sin x} \right)} \right|_0^{\frac{\pi }{2}} = 7\)

e) \(\int\limits_{\frac{\pi }{4}}^{\frac{\pi }{2}} {{{\cot }^2}xdx} = \int\limits_{\frac{\pi }{4}}^{\frac{\pi }{2}} {\left( {\frac{1}{{{{\sin }^2}x}} - 1} \right)dx} = \left. {\left( { - \cot x - x} \right)} \right|_{\frac{\pi }{4}}^{\frac{\pi }{2}} = - \frac{\pi }{2} - ( - 1 - \frac{\pi }{4}) = 1 - \frac{\pi }{4}\)

g) \(\int\limits_0^{\frac{\pi }{4}} {{{\tan }^2}xdx} = \int\limits_0^{\frac{\pi }{4}} {\left( {\frac{1}{{{{\cos }^2}x}} - 1} \right)dx} = \left. {\left( {\tan x - x} \right)} \right|_0^{\frac{\pi }{4}} = 1 - \frac{\pi }{4}\)

h) \(\int\limits_{ - 1}^0 {{e^{ - x}}dx} = - \left. {{e^{ - x}}} \right|_{ - 1}^0 = e - 1\)

i) \(\int\limits_{ - 2}^{ - 1} {{e^{x + 2}}dx} = \left. {{e^{x + 2}}} \right|_{ - 2}^{ - 1} = e - 1\)

k) \(\int\limits_0^1 {({{3.4}^x} - 5{e^{ - x}})dx} = \left. {\left( {3.\frac{{{4^x}}}{{\ln 4}} + 5{e^{ - x}}} \right)} \right|_0^1 = \frac{9}{{\ln 4}} + \frac{5}{e} - 5\)