3x - 5(3x - 7) = 2(x + 9) +45
3x-15x-35=2x+18+45
3x-15x=2x
-12x-2x=-10x
2007-04-12 07:38:17 · 7 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
solve for x only! sorry about that
2007-04-12 07:49:19 · update #1
First of all....The second line should be
3x - 15x PLUS 35 = 2x + 18 + 45
You have (-5) times (-7), so that becomes POSITIVE 35.
Then....
3x - 15x + 35 = 2x + 18 + 45
-12x + 35 = 2x + 63
-12x + 35 - 2x = 2x + 63 - 2x
-14x + 35 = 63
-14x + 35 - 35 = 63 - 35
-14x = 28
-14x / -14 = 28 / -14
x = -2
2007-04-12 07:44:22 · answer #1 · answered by Mathematica 7 · 4⤊ 0⤋
3x - 5(3x - 7) = 2(x + 9) + 45
3x - (15x - 35) = 2x + 18 + 45
3x - 15x + 35 = 2x + 63
- 12x + 35 = 2x + 63
- 12 + 35 - 2x = 2x + 63 - 2x
- 14x + 35 = 63
- 14x + 35 - 35 = 63 - 35
- 14x = 28
- 14x / - 14 = 28 / - 14
x = - 28/14
x = - 2
- - - - - - - - -
Check
3x - 5(3x - 7) = 2(x + 9) + 45
3(- 2) - 5[3(- 2) - 7] = 2(- 2 + 9 ) + 45
- 6 - 5[- 6 - 7] = 2(7) + 45
- 6 - 5[- 13] = 14 + 45
- 6 - [ - 65] = 59
- 6 + 65 = 59
59 = 59
- - - - - - - - -
When there is a ( - ) preceding a parenthesis
- (15x - 35) once the parenthesis is removed the signs change, so it becomes - 15x + 35
- - - - - - - -s-
2007-04-12 15:02:39 · answer #2 · answered by SAMUEL D 7 · 0⤊ 0⤋
In your second line you have a reversed sign: -35 should be +35.
3x - 5 (3x - 7) = 3x + (-5)(3x) + (-5)(-7)
3x - 5 (3x - 7) = 3x -15x +35
So 3x - 15x + 35 = 2x + 63 or -14x = 28 giving x = -2
2007-04-12 14:57:24 · answer #3 · answered by Astral Walker 7 · 0⤊ 0⤋
No Its wrong. in the second step it should be +35 since you are multiplying negative times a negative which should be positive.
so essentially.. it should be
3x-15x+35 = 2x+18+45
-10x = 45+ 18 - 35
-10x = 28
x = -2.8
2007-04-12 14:45:02 · answer #4 · answered by John Smith 2 · 0⤊ 2⤋
No.
3x - 15x + 35 = 2x +18 + 45
-12x + 35 = 2x + 63
-10x = 28
-x = 2.8
x = -2.8
2007-04-12 14:43:48 · answer #5 · answered by edward_otto@sbcglobal.net 5 · 0⤊ 4⤋
you started out right. Except that -5 x -7 = +35
so you need to get all your x values on one side and everything else on the other.
3x - 15x + 35 = 2x +63
so subtract 2x from both sides to get -14x + 35 = 63
then subtract -35 from both sides to get -14x = 28
Then divide both sides by -14x to get the value of x
so x = -2.
When in doubt plug your value back in for x and solve.
2007-04-12 14:50:46 · answer #6 · answered by Should be Working! 4 · 1⤊ 0⤋
Your answer has a couple of mistakes
3x - 15x + 35 = 2x + 18 + 45 is correct
Group like terms
-12x + 35 = 2x + 63
Subtract 35 to each side
-12x = 2x + 28
Subtract 2x from each side
-14x = 28
Divide each side by (-14)
x = -2
Above answer is incorrect because he added 2x to the left side rather than subtracting it.
2007-04-12 14:43:54 · answer #7 · answered by Jeffrey O 3 · 1⤊ 3⤋