16) Show that the tangents to the curve $y = 7x^3 + 11$ at the points where x = 2 and x = – 2 are parallel.

Slope of tangent = $\frac{dy}{dx} = 21x^2$
$\frac{dy}{dx} = 21x^2 = 21(2)^{2} = 21 \times4 = 84$
$\frac{dy}{dx} = 21x^2 = 21(-2)^{2} = 21 \times4 = 84$
Hence, we can say that both the tangents to curve $y = 7x^3 + 11$ is parallel