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May 30, 2015

Posted by **John** on Tuesday, November 13, 2007 at 5:57pm.

Both are Solve using the quadratic formula :

1) x^2-3x=7x-2

x^2-3x-7x+2=7x-7x-2+2

x^2-10x+2=0

x = 10 +- sqrt10^2 - 4(1)(2) / 2(1)

x = 10 +- sqrt100 - 8 / 2

x = 10 +- sqrt92 / 2

x = 10 +- 2sqrt23 /2

x = 5 +- sqrt23

x = 5 + sqrt23 and x = 5 - sqrt23

2) x^2-7x-1= -7

x^2-7x+7-1 = -7+7

x^2-7x+6 = 0

x = 7 +- sqrt7^2 - 4(1)(6) / 2(1)

x = 7 +- sqrt49-24 / 2

x = 7 +- sqrt25 / 2

x = 7 +- 5 / 2

x = 7+5 / 2 , x = 12 / 2 , x = 6

x = 7-5 / 2 , x = 2 / 2 , x = 1

- Algebra -
**DrBob222**, Tuesday, November 13, 2007 at 6:10pmThe second one looks ok. I think step 7 of problem 1 has an error.

- Algebra -
**John**, Tuesday, November 13, 2007 at 6:18pmOk so what I did was

x = 10 +- 2sqrt23 / 2

I divided 10 by 2 and 2 by 2

Thats how i got

x = 5 +- sqrt23

- Algebra -
**DrBob222**, Tuesday, November 13, 2007 at 8:54pm1) x^2-3x=7x-2

x^2-3x-7x+2=7x-7x-2+2

x^2-10x+2=0

x = 10 +- sqrt10^2 - 4(1)(2) / 2(1)

x = 10 +- sqrt100 - 8 / 2

x = 10 +- sqrt92 / 2**OK to here. See below.**

x = 10 +- 2sqrt23 /2

x = 5 +- sqrt23

x = 5 + sqrt23 and x = 5 - sqrt23

**x = (10+-sqrt 92)/2**

x = (10+-sqrt 2(46)/2

(What you are doing here is dividing 10 by 2, which is correct, as well as 2/2, which also is correct. What is NOT correct is dividing 46 by 2 (you are using the divisor of 2 twice but the divisor of 2 disappeared when you used it to divide the 10 and 2 of 2*46).

x = (5+-sqrt 46)

- Algebra -

- Algebra -
- Algebra -
**tamesha**, Tuesday, October 2, 2012 at 7:53pm7x-2=22.5