What is the solution set for the above equation?
Show Solution
This is typical SAT question which is not only testing on the... also on the ability of test taker to mark the correct answer.
The test taker’s needs to consciously remove the extraneous s...duced due to squaring the expression let us explain in detail.
Given
that 
To find the solutions, we typically simplify the equation by squaring both the sides




Since
is a quadratic equation, hence it
has two solutions, 18 and 3.
Most test takers stop at this step and mark option C. which is wrong.
In a challenging question like this we need to be conscious that
is
not a quadratic equation. Hence, it will not have two solutions. We need to
remove the extraneous solution.
So, plug-in both the values to check whether they satisfy the equation
or not.
By
plugging in
= 3 in
, we get
= 
=>
=
, which is not true
as square root of a number is always nonnegative.
Hence,
cannot be equal to 3.
By
plugging in
= 18 in
, we get
= 
=> 8 =
, which is true as square root of a
number is always nonnegative.
Hence,
= 18.
Therefore, the only solution to the given equation is 18, which is choice B.
Note: In the above method, we are solving it by converting the initial equation into a quadratic equation, but the initial equation is not quadratic. So, we need to be careful about plugging in the values back in the initial equation.

≤ 350, so
can be 310 as well.
that are at the distance of 5 units from 2 is 
from 2 is equal to 5 units.
≤ 350 is equivalent to
.