Question

390×410 find the product by fourth identity (x+a) (x+b)= x square +(a+b)x+ab​

Answer 1

Answer:

390 x 410

= (400 - 10)(400 + 10)

Using

(a - b)(a + b) = {a}^{2} - {b}^{2}

Here, a = 400 and b = 10

Therefore

(400 - 10)(400 + 10) = {400}^{2} - {10}^{2}

= 160000 - 100

= 159900

Answer 2

Answer:

390 x 410

= (400 - 10)(400 + 10)

Using

(a - b)(a + b) = {a}^{2} - {b}^{2}

Here, a = 400 and b = 10

Therefore

(400 - 10)(400 + 10) = {400}^{2} - {10}^{2}

= 160000 - 100

= 159900