solve for j: 100 = j²

Explanation:

Step1: Apply square - root property

Take the square root of both sides of the equation $100 = j^{2}$. We know that if $x^{2}=a$ ($a\geq0$), then $x=\pm\sqrt{a}$. So, $j=\pm\sqrt{100}$.

Step2: Calculate the square - root

Since $\sqrt{100} = 10$, then $j=\pm10$.

Answer:

$j = 10$ or $j=-10$