Question

Can someone help me?

Answer 1

18. A line perpendicular to the x-axis is a vertical line.

The equation of a vertical line is

x = k,

where k is the x-coordinate of every point on the line.
Since this vertical line goes through point (-10, 0.5), and this point has x-coordinate -10, then every point on the line has x-coordinate -10.
The equation is

x = -10

19.

$f(x) = \dfrac{2}{3}x - 1$

To find f(9), just replace x with 9 and evaluate the expression.

$f(9) = \dfrac{2}{3} \times 9 - 1$

$f(9) = \dfrac{18}{3} - 1$

$f(9) = 6 - 1$

$f(9) = 5$

20.

$\sqrt{128} =$

$= \sqrt{64 \times 2}$

$= \sqrt{64} \times \sqrt{2}$

$= 8 \times \sqrt{2}$

$= 8 \sqrt{2}$