sorry about that last post i wrote it wrong. my bad.
2007-05-27 17:56:08 · 3 answers · asked by tries to understand why/how 3 in Science & Mathematics ➔ Mathematics
We start with:
2x+3y = 12
Cube both sides:
8x³ + 36x²y + 54xy² + 27y³ = 1728
Rearrange and factor:
8x³ + 27y³ + 18xy(2x+3y) = 1728
Substitute known values for 2x+3y and xy:
8x³ + 27y³ + 18(-14)(12) = 1728
Multiply:
8x³ + 27y³ - 3024 = 1728
Add 3024:
8x³ + 27y³ = 4752
And we are done.
2007-05-27 18:08:17 · answer #1 · answered by Pascal 7 · 1⤊ 1⤋
(a+b)^3=a^3+b^3+3ab(a+b)
Therefore a^3+b^3=(a+b)^3-3ab(a+b)
Now8x^3+27y^3
=(2x)^3+(3y)^3
=(2x+3y)^3-3*2x*3y(2x+3y)
=(12)^3-18*(-14)(12)
=1728+3024
=4752 ans.
2007-05-28 02:37:11 · answer #2 · answered by alpha 7 · 0⤊ 0⤋
Two.
2007-05-28 01:04:11 · answer #3 · answered by Pillsbury D 2 · 0⤊ 2⤋