Question

397×399
using(x+a)(x+b)=x^2+(2ab)x+ab​

Answer 1

hey !!

397x399=(400-3)x(400-1)

here x = 400

        a = (-3)

         b = (-1)

(x+a)(x+b) = x^2 +(2ab)x +ab

               =    (400)^2+(2(-3)(-1))400+(-3)(-1)

              = 160000+2400+3

               = 162403

hence , 162403 is the required answer .