Formula:
[tex] a {}^{2} + {b}^{2} = {c}^{2} [/tex]
Plug in 21 for a, plug in 72 for b.
[tex] {21}^{2} + {72}^{2} = {c}^{2} [/tex]
Then you would get:
[tex]441 + 5184 = {c}^{2} [/tex]
Then add 5184 and 441
[tex]5625 = {c}^{2} [/tex]
Square root it.
and you'll get
[tex]75 = c[/tex]
I hope this helps
