Step-by-step explanation:
x²-y²=12
(x-y)(x+y)=12
but x-y=4
4(x+y)=12
x+y=12/4
x+y=3
lets make x the subject of the formula
x=3-y
since x-y=4
(3-y)-y=4
3-y-y=4
-2y=1
y=-1/2
then x=3-y
x=3-(-1/2)
x=(6--1)/2
x=7/2
therefore; x²+2xy+y
=(7/2)²+2×7/2×-1/2+(-1/2)
=49/4-7/2-1/2
=(49-14-2)/4
=33/4
=8.25
=8
7-3y=22
-7 -7
-3y=15
Divide by -3. y=-5
You just have to figure it where you can place 2 solid lines and get 10 triangles ( i can only get 9). Think about the pentagon in the middle of the triangles and see if somehow you can create more triangles using only the two straight lines.
D. 50% will be long haired and 50% short haired
