Algebra
- Thread starter speedyj
- Start date
a=2, b=-4, c=-3
a³ - 2b - 4c²
As before, start with the "Not thinking" line:
2³ -8x(-4) -4x(-3)²
now sort out the numbers:
8 not 6!!!! It's 2x2x2 = 4x2 = 8
+ 32 minus times a minus is a plus
- 36 do it carefully, (-3)² = +9, -4x9 = -36
= 4
This is the explanation on a website my daughter has been pointed to by her teacher.
a³ - 2b - 4c²
As before, start with the "Not thinking" line:
2³ -8x(-4) -4x(-3)²
now sort out the numbers:
8 not 6!!!! It's 2x2x2 = 4x2 = 8
+ 32 minus times a minus is a plus
- 36 do it carefully, (-3)² = +9, -4x9 = -36
= 4
This is the explanation on a website my daughter has been pointed to by her teacher.
Where'd you get -8x(-4) from then?
Its not my expression, I don't understand where that comes from either, it is on the website that my daughter was pointed to.
It looks wrong to me also.
I agree but the website shows different.
Where does the +32 come from?
it's -2 x 4, not -8 x -4
Exactly!
My original post was to confirm that the website is wrong, I consider myself pretty able when it come to mathematics but was surprised that a website run by a maths teacher could be wrong. I will let my daughter ask the question of that teacher on Moday when she returns to school.