please help mee!!!!!! xx
2007-10-16 02:43:42 · 8 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
a² + 4a - 21 = 0
(a + 7)(a - 3) = 0
a = - 7 , a = 3
2007-10-18 07:46:34 · answer #1 · answered by Como 7 · 0⤊ 0⤋
OK
a^2 + 4a - 21 = 0 ; factorize
(a+7) (a-3) = 0
a= -7 or 3.
Factoring seems to be an issue for you. The key to factoring is to use the FOILmethod (First ones, Outside then Inside, then Last ones). Note that when you multiply using the foil, a*a = a^2. a*-3 = -3a, then 7 *a = 7a (add these two you would have 4a), then 7*-3 = -21.
Hope this helps.
2007-10-16 09:58:59 · answer #2 · answered by pyz01 7 · 0⤊ 0⤋
Let's do this:
a(squared) + 4a = 21
That's a little bit easier
Let's try some numbers:
Could it be 2?
4 + 8 = 21....Nope, too low
How about 4?
16 + 16 = 21....Nope, to high
What about 3?
9 + 12 = 21....Ah ha! The answer is a=3
2007-10-16 09:49:29 · answer #3 · answered by Yoi_55 7 · 1⤊ 0⤋
-7 or 3
2007-10-16 09:56:50 · answer #4 · answered by fiboway 2 · 0⤊ 0⤋
a= -7, 3
2007-10-16 09:50:20 · answer #5 · answered by Anonymous · 1⤊ 0⤋
It will equal 2 things
(a-3)(a+7)=0
a= 3, a=-7
cidyah you copied the question down wrong in you answer - and so got the wrong values of a
2007-10-16 09:48:21 · answer #6 · answered by Anonymous · 1⤊ 0⤋
a^2-4a-21=(a-7)(a+3)
So, (a-7)(a+3)=0
a-7=0 implies a=7
a+3=0 i,plies a=-3
a=-3 , 7 (both are possible)
2007-10-16 09:47:57 · answer #7 · answered by cidyah 7 · 1⤊ 0⤋
Awww. that sucks, bro. :(
2007-10-16 09:46:41 · answer #8 · answered by Anonymous · 0⤊ 2⤋