Tuesday

October 21, 2014

October 21, 2014

Posted by **Lisa** on Friday, March 21, 2008 at 6:30pm.

solve the equation by factoring

35-x^2+2x=0

x^2 x^2

35+2x=x^2

-2x=-2x

35-35=x^2-2x-35

0=x^2-2x-35

(x-7)(x+5) (x-7)(x+5)

x-7=0 x+5=0

x=7 x=-5

(7)^2-2(7)-35 -5^2-2(-5)-35

49-14-35 25+10-35

0 0

Solution set is {-5,7}

- algebra -
**Reiny**, Friday, March 21, 2008 at 6:42pmfirst line: 35-x^2+2x=0

next important line: x^2-2x-35 = 0 , I don't know why you did all that other stuff in between.

(see my response to a similar problem in the reply to "Lori" two postings down from here)

so x^2-2x-35 = 0

(x-7)(x+5) = 0

then x=7 or x = -5

you had as factors (x-7)(x+5) (x-7)(x+5).

Why 4 of them?? It was only a quadratic, so it could have at most two factors.

- algebra -
**Anonymous**, Friday, March 21, 2008 at 6:48pmthat was from the example we were given, I just followed it. Our instructor was ill and the sub handed out examples, no one understood and the sub could not explain! Sorry I have the correct answers, but I need to go back and show my work the right way? I will look in my book. Thanks

- algebra -
**Reiny**, Friday, March 21, 2008 at 6:56pmHere is all you would have needed, down to the essential steps

35-x^2+2x=0 (multiply by -1 to get it in standard form

x^2 - 2x - 35 = 0 (this factors to)

(x-7)(x+5) = 0

therefore x-7 = 0 or x+5 = 0

therefore x = 7 or x = -5

If you are asked to verfy the solution, this is how you would do that:

if x=7, then

L.S. = 7^2 - 2(7) - 35

= 49 - 14 - 35 = 0

= R.S.

if x= -5

L.S. = (-5)^2 - 2(-5) - 35

= 25 + 10 - 35

= 0

= R.S.

Therefore x = 7 or x = -5

- algebra -

**Answer this Question**

**Related Questions**

Algebra - Solving quardratic equations using factoring. 2X^2+2X-4=0 The book ...

Algebra-Graphing Linear Equation - Y<2X+4 The way I unerstand from the book ...

Math - 2x(x+3) = 0 Is there a way to solve that using the below methods? ...

algebra 2 - solve this equation by factoring a^2-8a=-15 the a^2 is a' squared

Algebra - Use factoring to solve the equation: x^2+13x+36+0

Algebra - 6x^2+9cx= 6c^2 I tried moving the 6c^2 to the other side of the ...

algebra - Write the equation in quadratic form and solve it by factoring. x2(8x...

Algebra - Steps to factoring this x^3 - 8 ? I'm only used to factoring out the x...

Algebra - Solve the equation by factoring: 6y^2+7y-3=-12y^2-54y+4 The answers ...

Algebra - I am working on Factoring the Trinomial and need help to solve this ...