1st term =x, 2nd term =x², So the common difference d = x² - x
at the same time they are giving d=12, then: x² - x = 12 x² - x + 12 =0, solving it gives: x' =6 & x" = - 2 for x= - 2, then PA => -8, 4, 16 (d=12) ==> 3rd term = 16 & for x=6, then PA ==> 24, 36. 48, (d=12) etc 3rd term = 48
4X,X^2,_ Common difference=12 second term - first term=12 X^2-4x=12 subtract 12 from both sides X^2-4X-12=12-12 X^2-4X-12=0 now its a quadratic equation, so use either factor method or quadratic formula, X^2-6X-2X-12=0 take common x(X-6)-2(x-6)=0 x-2)(x-6)=0 so x is either 2 or 6 now use them to find the third term
