Firstly, subtract a^2 on both sides: [tex] b^2=c^2-a^2 [/tex]
Next, we are going to be using the difference of squares, which is [tex] x^2-y^2=(x+y)(x-y) [/tex] . Use this on the right side of the equation: [tex] b^2=(c+a)(c-a) [/tex]
Lastly, square root both sides of the equation, and your answer will be [tex] b=\sqrt{(c+a)(c-a)} [/tex]