i can't solve this question
[tex] if \: a = \sqrt{3} + \sqrt{2.} b = \sqrt{3} - \sqrt{2 \: } find \: the \: value \: of \: a {}^{2} - ab + b {}^{2} [/tex]

i cant solve this questiontex if a sqrt3 sqrt2 b sqrt3 sqrt2 find the value of a 2 ab b 2 tex class=