omg...why can't i do this....? (1 Viewer)

[efini4eva]

........not a hard question but i can't do it....;;

year 11 stuff....and i got hsc coming up...lol i'm screwed..... ( currently yr 12 )

x + 2 * square rooot (x+1) = 7

answer is 3....but i can't figure out steps.......

square root ( x+5 ) + square root (x-2) = squareroot (5x-6)

answer is 11......

spent 30 min....but....lol...can't do it...damn.

 

[Loz_metalhead]

Something is wrong..when you subsitutue the 3 in it doesnt = 7...Lol:S

 

[Dumsum]

First one, isolate the square root and square both sides.

2Sqrt(x+1) = 7-x
4(x+1) = 49 - 14x + x^2
4x + 4 = 49 - 14x + x^2

x^2 -18x + 45 = 0
(x-15)(x-3) = 0
x = 15 or 3

The 15 doesn't work considering it requires taking the negative answer for Sqrt(x+1), but square roots like that are defined to be positive, so the answer is x=3.

 

[Dumsum]

Something is wrong..when you subsitutue the 3 in it doesnt = 7...Lol:S

3 + 2Sqrt(3 + 1)
= 3 + 2Sqrt4
= 3 + 2*2
= 7

 

[Loz_metalhead]

I thought it was (x+2)^2(x+1)=7

Opps squared root..Lol. I only do 2U

 

[SaHbEeWaH]

alright my bad

 

[gman03]

sqrt(11+5) + sqrt(11-2) = sqrt(55-6)
4 + 9 = 7

this is a false statement

This is a false statement

sqrt(11-2) = sqrt (9) = 3, not 9

The original question asked for sqrt(x-2), not sqrt(x-1).

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(x+5)^0.5 + (x-2)^0.5 = (5x-6)^0.5

(x+5) + 2[(x+5)(x-2)]^0.5 + (x-2) = 5x - 6

2[(x+5)(x-2)]^0.5 = 3x - 9

4(x² + 3x - 10) = 9x² - 54x + 81

5x² - 66x + 121 = 0

x = 11/5 or 11

 

[efini4eva]

sqrt 16 + sqrt 9 = sqrt 49

4 + 3 = 7 trueeeeeeeeee eh?;;

btw thx dumsum!