The value of the following expression is : ((9·1)^2 − (10·9)^2) / ((9·1)^3 − (10·9)^3) × ((9·1)^2 + (9·1 × 10·9) + (10·9)^2) / ((7·9)^2 + (7·9 × 2·1) + (2·1)^2) × ((7·9)^3 − (2·1)^3) / ((7·9)^2 − (2·1)^2)