2007-11-04 12:42:08 · 7 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
To be factorised?
4x² - 4x - 15
(2x - 5)(2x + 3)
2007-11-04 20:34:13 · answer #1 · answered by Como 7 · 0⤊ 1⤋
Well using the grouping method, it's quite simple to solve this.
First, u multipy: 4 x -15 = -60
now we try to find what factors of -60 would equal -15, because -60 is negative we know that the factors must subtract from each other to equal 4. so we factor this {1,60)(2,30)(3,20)(4,15)(5, 12) (6,10) and the numbers that do this are 6 and 10, and in order to give a negative value 10 must be negative.
No that u got the number we group substituting the middle number(-4x) by the number we just got(-10,6)
4x^2-4x-15
(4x^2-10x)(6x-15)
now we just simplify
2x(2x-5) and 3(2x-5)
taking 2x, for the first group and 3 for the next grup
(2x+3)(2x-5)
by groping them again u have the answer
2007-11-04 12:59:26 · answer #2 · answered by ≡<S 1 · 0⤊ 0⤋
4x(squared) - 4x - 15
Factor the first and the last term:
4x^2 = 2x , 2x
-15 = -5 , 3
The combinations should give you the sum of the product of the means and extremes should be -4x.
(2x - 5) (2x + 3)
means = -5(2x) = -10x
extremes = 2x(3) = 6x
-10x + 6x = -4x
Answer: (2x - 5) (2x + 3)
2x - 5 = 0
Add 5 to both sides of the equation:
2x = 5
Divide both sides of the equation by 2
x = 2/5
2x + 3 = 0
Subtract 3 to both sides of the equation
2x = -3
Divide both sides of the equation by 2:
x = -3/2
Solution set: (2/5, -3/2)
2007-11-04 12:56:09 · answer #3 · answered by edith p 3 · 0⤊ 0⤋
I'm assuming you wish to factor it??
4x^2 - 4x - 15 = (2x + 3) (2x - 5)
2007-11-04 12:46:33 · answer #4 · answered by Linda K 5 · 0⤊ 0⤋
i think it would be 8x(cubed)-15 becuase it you and +4x to -4x that would canel out and u add +4x to 4x(squared) to balance out the equation.....
2007-11-04 12:48:17 · answer #5 · answered by Shynehtfd 1 · 0⤊ 0⤋
4x^2 -4x -15
x= ( -b ±sqrt(b² -4ac)) /2a
x = (+4 ±sqrt(16 -4*4*-15)) /2*4
x = (+4 ±sqrt(16 +240)) /8
x = (+4 ±sqrt(256)) /8
x = (+4 ±16) /8
x = (1/2) ±2
ANS:x = -1.5 or 2.5
2007-11-04 12:49:41 · answer #6 · answered by David F 5 · 0⤊ 0⤋
(2x+3)(2x-5)
2007-11-04 12:46:23 · answer #7 · answered by norman 7 · 1⤊ 0⤋