[tex]\mathsf{Given : a - b = 5}[/tex]
[tex]\mathsf{Squaring\;on\;both\;sides,\;we\;get :}[/tex]
[tex]\mathsf{\implies (a - b)^2 = 5^2}[/tex]
[tex]\mathsf{\implies a^2 + b^2 - 2(a.b) = 25}[/tex]
[tex]\mathsf{Given : a^2 + b^2 = 29}[/tex]
[tex]\mathsf{\implies 29 - 2(a.b) = 25}[/tex]
[tex]\mathsf{\implies 2(a.b) = 29 - 25}[/tex]
[tex]\mathsf{\implies 2(a.b) = 4}[/tex]
[tex]\mathsf{\implies (a.b) = 2}[/tex]
