Rajah 3 years ago √(x+4)+√(2x+6)=7

1. oojih.com

rsmith almost gets the question right. (a+b)^2 = a^2 + 2ab + b^2,

2. oojih.com

this is how I'd approach it: $\sqrt{x+4} = 7 - \sqrt{2x+6}$ $x+ 4 = 49 + (2x+6)-14 \sqrt{2x+6}$ $x + 4 -49 -2x-6=-14\sqrt{2x+6}$ $-x -51 = -14\sqrt{2x+6}$ $x+51 = 14\sqrt{2x+6}$ I am sure you can continue and solve this equation now.

3. oojih.com

@ rsmith, you can validate whether your answer is correct by plugging x=13 into the equation sqrt(13+4) + sqrt(2*13+6) =7 sqrt(17) + sqrt(32) = 7 ?

4. alice_smith

dont u got to do the one and the ( and here first then u have to to keep bringing it down

5. alice_smith

till u get ur answer or change keep oppisite

6. rsmith

@oojih where are you going with your solution?

7. alice_smith

i think am right yay

8. estudier

Just square both sides: 3x+10+ 2 sqrt(......=49) etc etc.

9. oojih.com

@ rsmith, you need to square the equation one more time to get rid of the square toot, then it boils down to a quadratic equation whic looks prett nasty from the number.

10. alice_smith

11. alice_smith

u confuse me

12. rsmith

yes x^2 + 102x + 2601 = 196(2x+6) does look nasty

13. alice_smith

am correct

14. oojih.com

$x+ 51 = 14 \sqrt{2x+6}$ $(x+51)^2 = 14^2 (2x+6)$ yes..mr rajah can solve this fun quadratic equation

15. oojih.com

check out http://www.oojih.com/displaypage/algebra/ for more algebra study guide and practice test.

16. rsmith

x^2 - 290x +1425 = 0

17. rsmith

you are right oojih. :) roots are 285 and 5. 285 is not sensible so the root being 5 works

18. oojih.com

sqrt(5+4) + sqrt(2*5+6) =7 sqrt(9) + sqrt(16) = 3 + 4 = 7... yaayy, good job rsmith

19. oojih.com

I command you for solving the quadratic equation..:) This is a good math question, but the number should be made simpler so that students get the concept instead of being bogged down by this ugly number.

20. rsmith

true that