Sunday, February 19, 2012

Questions About How To Factor By Grouping

George asks…

How do you do factor by grouping?

How do you solve this by factor by grouping?

0 = x^3 + 4x^2 -3x - 18

According to my calculator, the roots are (2,0) once and (-3,0) twice.. How can I reach that answer?

admin answers:

X³ + 4x² - 3x - 18 = 0
x³ + 4x² - 12x + 9x - 18 = 0
x(x²+4x-12) + 9(x-2) = 0
x(x+6)(x-2) + 9(x-2) = 0
(x-2)[x(x+6)+9] = 0
(x-2)(x²+6x+9) = 0
(x-2)(x+3)(x+3) = 0

x = 2, -3 (twice)

Nancy asks…

How do you factor x(a+2) - 2(a+2) by the grouping method?

x(a+2) - 2(a+2) Need to factor by grouping. If anyone could help, I would greatly appreciate it!

admin answers:

(a+2) is the common factor; so
(a+2) * (x-2) is the answer

Sandy asks…

How do you factor by grouping?

How would you solve the equation 10x^3+20x^2+x+2

How would you go about solving this? I mean I understand how to create the pairs, but I don't understand the part about the greatest common factor. Could you help me please?

admin answers:

If you factor by grouping, you will prevail

Ken asks…

How do you factor by grouping x^2-y^2-10y-25?

the asnwer (x-y-5) (x+y+5)

i need a step by step guide to how to get to this answer

thank you

admin answers:

X^2 - y^2 - 10y - 25

= x^2 - (y^2 + 5y + 5y + 25)

= x^2 - (y (y + 5) + 5 (y + 5))

= x^2 - (y + 5) (y + 5)

= x^2 - (y + 5)^2 . . . . Difference of squares:

= (x - (y + 5)) (x + (y + 5))

= (x - y - 5) (x + y + 5)

Maria asks…

How do you "factor by grouping" in Pre-Calc?

How do you "factor by grouping" in Pre-Calc?

My pre-calc packet asks me to "factor by grouping".. and I am a bit confused.

Here are some of the questions that tell me to "factor by grouping":
1. x^3 - x^2 + 2x - 2
2. 2x^3 - x^2 - 6x + 3
3. 6x^3 - 2x + 3x^2 - 1

If you could explain it to me it would really help, thanks!

admin answers:

Question 1
x ³ + 2 x - (x ² + 2)
x (x ² + 2) - (x ² + 2)
(x - 1) (x ² + 2)

Question 2
2 x ³ - 6 x - x ² + 3
( 2 x )( x ² - 3 ) - ( x ² - 3 )
( x ² - 3 ) ( 2 x - 1 )

Question 3
( 3 x ² )( 2 x + 1 ) - ( 2 x + 1 )
( 2 x + 1 ) ( 3 x ² - 1 )

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