Question

evaluate (402)^2-(398)^2​

factorise

Answer 1

Step-by-step explanation:

402^2- 398^2

402^2

(400+2)  [ (a + b)^2 = a^2 + 2ab +b^2 ]

(400+2)= 400^2 + 2 * 400 * 2 + 2^2

             =80000 + 1600 + 4

            = 81604

398^2

(400 - 2)  [ (a - b)^2 = a^2 - 2ab +b^2 ]

(400 - 2)= 400^2 - 2 * 400 * 2 + 2^2

             =80000 - 1600 + 4

            = 78,404

=81604 - 78404

=3200

Answer 2

Answer:

3200

Step by step explanation:

402^2- 398^2

402^2

(400+2)  [ (a + b)^2 = a^2 + 2ab +b^2 ]

(400+2)= 400^2 + 2 * 400 * 2 + 2^2

=80000 + 1600 + 4

= 81604

398^2

(400 - 2)  [ (a - b)^2 = a^2 - 2ab +b^2 ]

(400 - 2)= 400^2 - 2 * 400 * 2 + 2^2

=80000 - 1600 +

 = 78,404

=81604 - 78404

=3200