2006-09-27 16:31:45 · 12 answers · asked by jelliejones06 1 in Science & Mathematics ➔ Mathematics
You can write:
x^2 + 8x + 15 = X^2 + 5x + 3x + 15 [Because 15 can be factored as 5 into 3 and 5 + 3 = 8]
Now x^2 + 5x + 3x + 15 = x(x + 5) + 3(x + 5)
= (x + 5)(x + 3). We are done!
2006-09-27 16:38:15 · answer #1 · answered by quidwai 4 · 1⤊ 0⤋
YOU CAN FACTORIZE BY SPLITTING THE MIDDLE TERM.
X2+8X+15
AS 5 AND 3 MAKE A SUM OF 8 PRESENT IN THE MIDDLE AND A PRODUCT OF 15 PRESENT IN THE LAST PLACE
=X2+5X+3X+15
=X(X+5)+3(X+5)
=(X+3)(X+5)
FACTORS= -5 AND -3
2006-09-27 19:17:53 · answer #2 · answered by Anonymous · 0⤊ 0⤋
When factoring
X² + 8x + 15
Ask what factors add to 8
ask what factors when multiplied equal 15
15/3 Because 15 divided by 3 equals 5
5/5 Because 5 divided by 5 equals 1
The factors are 3 and 5
3 x 5 equals 15 and 3 + 5 equals 8
- - - - - - - - - - - - - - - - - - - - - - - - - - -
x² + 8x + 15
(x + 5)(x + 3)
2006-09-28 00:46:28 · answer #3 · answered by SAMUEL D 7 · 0⤊ 0⤋
x2 +8x + 15
= x2 + 5x + 3x + 15 (coz 15 = 5X3 and 8 = 5+3)
= x(x+5) + 3(x+5)
= (x+3)(x+5)
2006-09-27 16:36:16 · answer #4 · answered by robokid 2 · 0⤊ 0⤋
We have:
(x + a)(x+b)
=X2 + bx +ax+ ab
=X2 + x(a+b)+ ab
Now we can apply this:
X2 +8x+15
=X2 + x(3+5)+3*5
=X2 + 5x+3x+ 15
=x(x+5)+3(x+5)
=(x+3)(x+5)
I hope it helped. Good luck in Math :D
2006-09-27 19:44:44 · answer #5 · answered by Anonymous · 0⤊ 0⤋
find all the factor combinations of +15
-1 -15
1 15
-3 -5
3 5
find out which pair can be added to make 8
(X+3)(X+5)
FOIL
X^2+5X+3X+15 = X^2+8X+15
2006-09-27 16:53:14 · answer #6 · answered by Adam 2 · 0⤊ 0⤋
x2 + 8x+ 15 =
x2 + 5x+3x+15=
x(x+5)+3(x+5)=
(x+3)(x+5)
ANS:(x+3)(x+5)
2006-09-27 17:20:49 · answer #7 · answered by ssrirag2001 2 · 0⤊ 0⤋
the answer would look like this
(x+a)(x+b)
to get a and b, think of 2 numbers that has a sum of 8 and a product of 15.
that would be 5 and 3
so a and b will be 5 and 3,respectively.
so the answer would be
(x+5)(x+3)
2006-09-27 16:48:56 · answer #8 · answered by lois lane 3 · 0⤊ 0⤋
What factors of 15 add to 8?
5 times 3 is 15
5 plus 3 is 8
(x+5)(x+3)
Pretty easy, huh?
SWEETIE: Please don't vote 10 times for yourself. I've noticed that all of your best answers (with the exception of the ones that are chosen by the asker) have 10 votes. I know there are not 10 people voting for your answer, so that means you have multiple accounts...
2006-09-27 16:33:02 · answer #9 · answered by MsMath 7 · 1⤊ 0⤋
Well dear,
you should find 2 numbers as 'a' & 'b' which when you add them the result would be 8 & when u multiply them the result would be 15 ...
(x + a) ( x + b)
a + b = 8
a * b = 15
a = 3 & b = 5
( x+ 3 )(x +5)
Good Luck ...
2006-09-27 22:27:08 · answer #10 · answered by sweetie 5 · 2⤊ 1⤋