I'm stuck with this problem..
How do I factor it?!
27x^3 + 64
Thanks in advance for you math geniuses out there. :)
2007-04-23 02:57:47 · 2 answers · asked by Arron 2 in Science & Mathematics ➔ Mathematics
It's the sum of 2 cubes:
Recall x³+y³ = (x+y)(x²-xy+y²).
So 27x³+64 = (3x+4)(9x²-12x+16).
It helps to remember that x+y is always a factor
of x³+y³. You can always get the other factor
by long division if you forget it.
2007-04-23 03:10:36 · answer #1 · answered by steiner1745 7 · 2⤊ 0⤋
This one is easy!
27x^3 + 64 = 0, so
27 x^3 = -64
now take cube roots or everything, notice that cube root of 27 is 3 and cube root of -64 is -4, so we get
3x=-4, and so x = -4/3.
Alternatively once we get
27 x^3 = -64 gives
x^3 = -64 / 27.
Put cube root (-64/27) into calculator. Ans will be -4/3.
To check, put x = -4/3 into original equation. Use your calculator to check that it's correct. ... Good luck!
2007-04-23 10:02:42 · answer #2 · answered by emin8r 2 · 0⤊ 3⤋