Why is the middle term 2ab in (a+b)^2 and -2ab in (a-b)^2 when written in standard form

Step-by-step explanation:

You can try to expand, then you will get the middle term as 2ab or -2ab:

(a+b)² = (a+b)(a+b)

= a² + ab + ab + b²

= a² + 2ab + b²

As for the (a-b)², it will come in the same way :

(a-b)² = (a-b)(a-b)

= a² - ab - ab + b²

= a² - 2ab + b²

(Hope you can understand)

16.9 times 2.85

step-by-step explanation:

225x²+4=0

225x²=0-4

225x²=-4

x²=-4/225

x=±√-4/225