Using identity (a-b)²=a²-2ab+b² (198)²

Question

How to do (198)² by using identity (a-b) ²=a²-2ab+b²

Answer 1

Good morning Precilla,

 

you want to set 198 equal to one number minus another as something that will be easy to work with.

 

It's close to 200 so lets use (200 -2)

 

198 = 200-2

 

if we're using (200-2), then a =200 and b = 2

 

(200-2)² = 200² -2(200)(2) + 2²

 

 = 40,000 - 800 + 4

 

 = 39,204