Question

Help me and get 40 points.
Find 98² and 390² by this identity
(a-b)² =a²-2ab+b²

Answer 1

$\huge\mathcal{Heya!!}$

Identity should be used :-

(a - b)² = a² + b² - 2ab

1. 98²

This can also be written in the form :-

(100 - 2)²

On further solving by applying the identity

Here, a = 100 and b = 2

= (100)² + (2)² - 2(100)(2)

= 10000 + 4 - 400

= 10004 - 400

= 9604



2. 390²

This can also be written in the form :-

(400 - 10)²

On further solving by applying the identity

Here, a = 400 and b = 10

= (400)² + (10)² - 2(400)(10)

= 160000 + 100 - 8000

= 160100 - 8000

= 152100

$\huge\tt{Verification \ :-}$

1. 98² = 98 × 98 = 9604

2. 390² = 390 × 390 = 152100

$\huge\mathbb{Hope \ this \ helps.}$

Answer 2

$\bold{\boxed{HEY!!!}}$




$<B><I>HERE IS YOUR ANSWER :-$




Identity => ( a - b )² = a² - 2ab + b²



98² = ( 100 - 2 ) ²



comparing with the identity



a = 100 & b = 2



98² = ( 100 - 2 )²



= 100² - 2 ( 100 )( 2 ) + 2²



= 10000 - 400 + 4



= 9600 + 4



= 9604



98² = 9604



390² = ( 400 - 10 )²



= 400² - 2 ( 400 )( 10 ) + 10²



= 160000 - 8000 + 100



= 152000 + 100



= 152100



390² = 1,52,100