If (x - 3)^2 = 225, which of the following could be the

Question

If (x - 3)^2 = 225, which of the following could be the value of x + 3 ?

(A) -15
(B) -12
(C) -9
(D) 15
(E) 18

in this question if we take the square of both sides we have\(x - 3= 15\)so why the explanation says: \(x - 3 = 15\) and \(x - 3 = -15\) ????? :help2

KarishmaB · Accepted Answer

Honestly carcass, that's a newbie mistake and you should not be making it!

(x - 3)^2 = 15^2

When you take the root, you get 
|x-3| = 15
and hence you get x = 18 or -12

Alternatively, 
 (x - 3)^2 - 15^2 = 0 
(x - 3 - 15)(x - 3 + 15) = 0
x = 18 or -12

jbisht · Answer

both 18 and -12 satisfy the given equation

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jbisht · Answer

hence, x+3 is 21 or -9

Posted from my mobile device

Carcass · Answer

dumb mistake

thanks

shanmugamgsn · Answer

Yes here are my two cents...

(x - 3)^2 = 225

Since squaring on both sides leaves +/-  x - 3 = +/- 15 
This gives two eqns..
  x - 3 = 15  
  x - 3 = -15

So, x= 18 means x+3=15
or 
x=-12 means x+3=-9

Carcass · Answer

No no .......you are perfectly right

. maybe tired maybe stressed..........I know but you are right. Thanks

PareshGmat · Answer

One more method (This is time consuming)

Writing the equation as

x^2 - 6x + 9 - 225 = 0

x^2 - 6x + 9 - 216 = 0

(x-18) . (x+12) = 0

x = 18 OR x = -12

x+3=15 or x+3 = -9

stonecold · Answer

Nice..!!!!!
Here 15^2=225
But -15^2=225 too
Hence x+3 can be 18+3=21 or -12+3=-9
Smash that C

AnisMURR · Answer

x-3 = 15

or

x-3= -15

So x=18 or x=-12

x+3=21 or x+3=-9
 
 So Answer B

Pm091989 · Answer

How we can confirm which answer to be considered?

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Vinayak Shenoy · Answer

(x-3)^2= 225
(x-3)^2= 15^2
(x-3)= +15 or -15
x=18 or -12
now the question asks which could be the value of x+3
if x=18 ==> x+3=21 (could be)
if x=-12==> x+3= -9 (could be)

only-9 is available as an option.
If both -9 and 21 were available as individual options then the question would be wrong.

Abhishek009 · Answer

\sqrt{(x - 3)^2} = \sqrt{225}

Or,  ( x - 3 ) =   +   15

If x = +15

x - 3 = 15

Or, x = 18 so x + 3 = 21

If x - 3 = - 15

Or, x = -12 , so  x + 3 = -9

Hence, answer will be (C) -9

JeffTargetTestPrep · Answer

We can start by taking the square root of both sides of the equation (x - 3)^2 = 225.

√(x - 3)^2 = √225

x - 3 = 15 or x - 3 = -15

Thus, x = 18 or -12.

So possible values of x + 3 are as follows:

18 + 3 = 21

-12 + 3 = -9

Since -9 is the only answer within the answer choices, the answer is C.

Answer: C

GMATinsight · Answer

(x - 3)^2 = 225
i.e. x-3 = +15 or -15
i.e. x = +18 or -12
i.e. x+3 = +21 or -9

Answer: option C

hareesh555 · Answer

Step 1 :

(x-3)^2 = X^2 +9-6x

Step 2:

As per the question given , Replace the above i.e , X^2 +9 - 6X = 225

X^2 - 6X - 216 =0

Step 3:

X^2 -18X+12 X -216 = 0. ( 216 = 18*12)

Therefore we get, X = either 18 or -12 .

S0 , -12+3 = -9 . Answer

Subhrajyoti · Answer

(x-3)^2= 225, so it means if i put x=-12 then i will get (-12-3)^2=225, thus x+3= -12+3=-9

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If (x - 3)^2 = 225, which of the following could be the

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