Solve ∫ (from - 2 to - 1) of -2x-x^2

$$\int _ { - 2 } ^ { - 1 } - 2 x - x ^ { 2 }$$

Evaluate

$$\frac{2}{3}\approx 0.666666667$$

Solution Steps

Evaluate the indefinite integral first.

$$\int -2x-x^{2}\mathrm{d}x$$

Integrate the sum term by term.

$$\int -2x\mathrm{d}x+\int -x^{2}\mathrm{d}x$$

Factor out the constant in each of the terms.

$$-2\int x\mathrm{d}x-\int x^{2}\mathrm{d}x$$

Since \int x^{k}\mathrm{d}x=\frac{x^{k+1}}{k+1} for k\neq -1, replace \int x\mathrm{d}x with \frac{x^{2}}{2}. Multiply -2 times \frac{x^{2}}{2}.

$$-x^{2}-\int x^{2}\mathrm{d}x$$

Since \int x^{k}\mathrm{d}x=\frac{x^{k+1}}{k+1} for k\neq -1, replace \int x^{2}\mathrm{d}x with \frac{x^{3}}{3}. Multiply -1 times \frac{x^{3}}{3}.

$$-x^{2}-\frac{x^{3}}{3}$$

The definite integral is the antiderivative of the expression evaluated at the upper limit of integration minus the antiderivative evaluated at the lower limit of integration.

$$-\left(-1\right)^{2}-\frac{\left(-1\right)^{3}}{3}-\left(-\left(-2\right)^{2}-\frac{\left(-2\right)^{3}}{3}\right)$$

Simplify.

$$\frac{2}{3}$$