Even if you were rushing and did not rephrase the target question in conjunction with the Given condition (you weren’t exactly thinking clearly *ahem*), this is a good question to think about a combination of topics.
From the question stem alone, you can see that the question asks for the Square of a Difference:
What is: (M - 2)^2 ?
s1: N = 20
Since we can find the value of M as = 22, we can solve.
S2: (N)^2 = 400
You can take the square root of both sides, in which case the absolute value of N = 20
And
N = +20
or
N = (-20)
If N = 20 —> M = 22
If N = (-20) —> M = (-)18
*Q*
What is: (M - 2)^2 = ?
The concept is that when you square a nonzero number, the magnitude of that number is all that matters for purposes of finding the result.
Whether the number is negative or positive is irrelevant: all we care about is the magnitude (in other words, the absolute value of that number ….. which is that number’s distance from 0 on the number line)
In this case: (M - 2)^2 = ?
Any two corresponding values of M that are equidistant from +2 on the number line will produce the same output.
e.g., try values (-1) and +5— both 3 units away from 2 on the number line
You will get the same answer as: (3)^2 = 9
Taking this concept forward, we have two possible values of M: +22 , (-)18
Since both are 20 units away from +2 on the number line, you will end up with the same value when you solve for (M - 2)^2:
(20)^2 = 400
OR
You can just be more careful in the future and always remember to rephrase the question stem in the first step.
D
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