Question

Write down x+y+z whole square formula.

Answer 1

(x+y+z)^2=x^2+y^2+z^2+2(xy+yz+zx)

Answer 2

To square the sum of two unknown quantities, the formula we use is

$x+y^2=x^2+y^2+2xy$   ---(1)  

Now we have three unknown quantities, x, y,z

So, to get the formula for square of the sum of three unknown quantities, we need to follow the steps

Step 1: Substitute (x+y)  instead of x in (1) and z instead of y, we get

$((x+y)+z)^2=(x+y)2+z^2+2(x+y)z=(x+y)2+z^2+2xz+2yz$    

Step 2: Expand first term using (1)  

$((x+y)+z)^2=x^2+y^2+2xy+z^2+2xz+2yz$    

Step 3: Rearrange the terms by grouping with same exponents and also in the descending order of the exponent of each variable

$(x+y+z)^2=x^2+y^2+z^2+2xy+2xz+2yz$