English Deutsch Français Italiano Español Português 繁體中文 Bahasa Indonesia Tiếng Việt ภาษาไทย
All categories

The problem is 25x(squared) - 30x = -9

The choices for the answer are:

x= 3/5
x= 5/3
x= -5/3
x= -3/5

2006-11-25 12:05:19 · 6 answers · asked by Anonymous in Science & Mathematics Mathematics

6 answers

x= 3/5

If you factor by grouping you would get
25x^2 - 15x -15x + 9 = 0

then you would factor the first two terms and the last two terms
5x(5x-3) -3(5x-3) = 0

use the terms outside the parentheses are one factor and the one inside the parentheses as the second factor
(5x-3)(5x-3) = 0

set to zero
5x-3 = 0

do algebra
x=3/5

or you could have just noticed that that equation is a perfect square

2006-11-25 12:13:45 · answer #1 · answered by Patrick 2 · 0 0

Ok this is a classic case of (A + B)^2 = A^2 + 2AB + B^2.

In this case A = 5x because sqrt(25x^2) = 5x or -5x and B is -3 because sqrt(9) = 3 or -3. 2*5x*-3 also equals -30. In fact if you want to be weird it is also (-5x + 3)^2 but we normally write it so that the first term is positive.

Anyway (5x -3)^2 = 0, so (5x - 3) = 0, so 5x = 3, so x = 3/5.

2006-11-25 12:13:25 · answer #2 · answered by Edgar Greenberg 5 · 1 0

25x^2 - 30x + 9 = 0
(5x - 3)^2 = 0
5x - 3 = 0
5x = 3
x = 3/5

2006-11-25 12:09:16 · answer #3 · answered by bgdddymtty 3 · 1 0

set it equal to zero, so 25x2-30x+9=0. Then you find something that multiplies to the the product of the first and last coefficients, and adds to the middle one. So something that multiplies to 225 and adds to -30.

This would be -25 and -5

You can factor it using these two numbers to help you out.

2006-11-25 12:23:47 · answer #4 · answered by Erik N 2 · 0 0

25x2-30x=-9
25x^2-30x+9=0
(5x-3)^2=0
5x-3=0
x=3/5

2006-11-25 13:05:59 · answer #5 · answered by yupchagee 7 · 0 0

(5x-3)^2
x= 3/5

2006-11-25 12:07:43 · answer #6 · answered by      7 · 0 0

fedest.com, questions and answers