Question

21-25 Use the form of the definition of the integral given in Theorem 4 to evaluate the integral.
23. $\int_{-2}^{0}\left(x^{2}+x\right) d x$

Answer 1

$\displaystyle \int^0_{-2} (x^2 +x )~dx\\\\\\=\displaystyle \int^0_{-2} x^2~ dx +\displaystyle \int^0_{-2}x ~ dx\\\\\\=\dfrac 13 \left[x^3 \right]^{0}_{-2}+ \dfrac 12 \left[ x^2\right]^{0}_{-2}\\\\\\=\dfrac 13 (0+8) + \dfrac 12 (0-4)\\ \\\\=\dfrac 83 - \dfrac 42\\\\\\=\dfrac 83 - 2\\\\\\=\dfrac 23$