Question

evaluate the following by using suitable identity ( )
a) 202 x 205 b) 99^2​

Answer 1

Answer:

a) (200+2)(200+5)= 200^2 +(2+5)200+(2×5)= 40000+ 1400+10= 41410 b) (90+9)^2 = 90^2+9^2+2×90×9= 8100+81+1620 = 9801

Explanation:

hope it will help please like the answer

Answer 2

$\sf\huge\bold{\underline{\underline{{Solution}}}}$

Formula used here :

$\sf \boxed{(x + a)(x - b) = {x}^{2} + (a + b)x + ab}$

$\sf \boxed{ {(a - b)}^{2} = {a}^{2} + {b}^{2} - 2ab }$

a) 202×205

it can also be written as :200+2 ×200+5

=>(200+2)(200+5)

it is in the form of (x+a)(x+b)

here,x=200 ,a=2 and b =5

=>(200)²+(2+5)200+(2×5)

=>40,000+7×200+10

=>40,000+1400+10

=>41410

∴202×205=41410

b)99²

=>(100-1)²

it is in the form of.(a-b)² where ,a=100 and b=1

=> (100)²+(1)²-2(100)(1)

=>10,000-200+1

=>9800+1

=>9801

∴99²=9801