Sagot :
Answer:
1. y=x²+2x+1
> y+?=(x²+2x+(2/2)²)+1
> y+1=(x²+2x+1)+1
> y+1=(x+1)²+1
> y=(x+1)²+1-1
> y=(x+1)²
2. y=4x²-4x+1
> y+?=4(x²-x+(-1/2)²)+1
> y+1/4=4(x²-x+1/4)+1
> y+4(1/4)=4(x-1/2)+1
> y=4(x-1/2)+1-1
> y=4(x-1/2)²
3. y=(x-3)(x+7)
> y+?=x²+4x-21
> y+?=(x+4x+(4/2)²)-21
> y+4=(x+4x+4)-21
> y+4=(x+2)²-21-4
> y=(x+2)²-25
4. y=x(x-9)
> y=x²-9x
> y+?=(x²-9x+(-9/2)²)
> y+?=x²-9x+81/4
> y+81/4=(x-9/2)²
> y=(x-9/2)²-81/4
5. y=x²-2x-48
> y=(x²-2x+(-2/2)²)-48
> y+?=(x²-2x+1)-48
> y+1=(x-1)²-48-1
> y=(x-1)²-49