factorise 7mn-21m²n²
Answers
Answer:
TAKING OUT THE COMMON FACTORS
When each term of a given expression contains a common factor, divide each term by this factor and enclose the quotient within brackets, keeping the common factor outside the bracket.
Procedure:
* Find the H.C.F of all the terms of the given expression.
Eg: 6a^2-3ax =3a{6a^2/3a-3ax/3a} Ans=3a(2a-x)
GROUPING METHOD
An expression of an even number of terms, may be resolved into factors, if the terms are arranged in groups such that each group has a common factor.
Procedure:
*Group the terms of the given expression in such a way that each group has a common factor.
*Factorise each group formed.
*From each group, obtained in step 2, take out the common factor.
Eg: ab+bc+ax+cx
=(ab+bc)+(ax+cx)
=b(a+c)+x(a+c)
Ans=(a+c)(b+x)
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