Question

The distance between $M(-1,5)$ and $N(x,5)$ is $8$ units. The value of $x$ is:

• A. $-9$ or $9$
• B. $-7$ or $9$
• C. $-9$ or $7$
• D. $-7$ or $-9$

Answer 1

The correct option is C $-9$ or $7$

$\sqrt{[x-(-1){]}^2+(5-5{)}^2}=8$

$\Rightarrow (x+1{)}^2=8^2\Rightarrow x+1=\pm 8$

$\therefore x=-9,7$