What must be added to the expression 21m2 + 4m to make it a perfect square? Click here to get the question
Solution
21m2 + 4m
Step1
Since the coefficient of m2 is 21, we first
divide through by 21 to make the coefficient of m2 to be 1
21m2/21 + 4m/21
= m2 + 4m/21
Step2
Coefficient of m is 4/21
Thus, what must be added is the
square of half of the coefficient of m, which is 4/21
Half the coefficient and square
it as follows
4/21* 1/2
= 2/21
Square of the halved coefficient
is (2/21)2 = 4/441
Thus, 4/441 must be added to
to make it a perfect square
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