Nigerian Scholars » » Joint Admissions and Matriculation Board (JAMB) Past Question

Find the area bounded by the curves $$y = 4 - x^2$$ and $$y = 2x + 1$$

Question

Find the area bounded by the curves $$y = 4 - x^2$$ and $$y = 2x + 1$$

Options

A) $$20\frac{1}{3}$$ sq. units

B) $$20\frac{2}{3}$$ sq. units

C) $$10\frac{2}{3}$$ sq. units

D) $$10\frac{1}{3}$$ sq. units

Explanation:

$$y = 4 - x^2$$ and $$y = 2x + 1$$
$$\Rightarrow 4 - x^2 = 2x + 1$$
$$\Rightarrow x^2 + 2x - 3 = 0$$
$$(x+3)(x-1) = 0$$
Thus, $$x = -3$$ or $$x = 1.$$

Integrating $$x^2 + 2x - 3$$ from $$(-3$$ to $$1)$$ with respect to $$x$$ will give $$\frac{31}{3} = 10\frac{1}{3}$$

Dicussion (1)

• $$y = 4 - x^2$$ and $$y = 2x + 1$$
$$\Rightarrow 4 - x^2 = 2x + 1$$
$$\Rightarrow x^2 + 2x - 3 = 0$$
$$(x+3)(x-1) = 0$$
Thus, $$x = -3$$ or $$x = 1.$$

Integrating $$x^2 + 2x - 3$$ from $$(-3$$ to $$1)$$ with respect to $$x$$ will give $$\frac{31}{3} = 10\frac{1}{3}$$