(x-y) 2 <i.e. squared>. Expand and simply

[Erebus]

'cos I can't!
=(x-y)(x-y)
= um... x2 -xy -yx -y2
....um..?

Help!

Yes - you are right. It simplifies to:

x2-2xy-y2

google distributive law

Isn't it
x2-2xy + y2 ?

Actually it is

x2-2xy+y2

because a negative squared is positive.

of course +y2

Expands to x(x-y) -y(x-y)
= x2 -xy -xy + y2
= x2 -2xy + y2
If that helps at all!

Thanks!

My Year 7 son uses the mnemonic FOIL to multiply out brackets.

so for (x-y)(x-y) you would do

Front x times x = x squared
Outer x times -y = -xy
Inner -y times x = -xy
Last -y times -y = y squared

which then ends up as

xsquared -2xy + ysquared

That's really helpful, too, Kings- I'll put that to DS1, as all methods are useful.

Or make a smiley face - above the equation draw a line linking both things at the beginning of each bracket and another line linking both terms at end of the brackets, so x to x and y to y - these are eyebrows.

Underneath a small line links y in first bracket and x in second, under that line a final line joins x in first bracket to y in second. These are the nose and mouth.

Like this

yy to the "smiley face technique". I teach it to my students and remind them that "we don't want any mono-brows" which they enjoy and it helps to make it stick!

We used to draw a bird with a big beak when I was at school
So for (a + b)(c+d)
The top of the beak would be an upward curve from a-d and a smaller curve from b-d.
The bottom of the beak would be a downward curve from a-c and a smaller curve from b-c.
Then the birds head is a circle to the left of the equation.