Question

5 Expand the following :
(2x–y+3z)²
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Answer 1

Answer:

(−2x+5y−3z) 2 is of the form (a+b+c) 2(a+b+c) 2

=a 2 +b 2 +c 2 +2ab+2bc+2ca

where a=−2x,b=5y,c=−3z

∴(−2x+5y−3z)

2=(−2x) 2 +(5y) 2 +(−3z) 2

2(−2x)(5y)+2(5y)(−3z)+2(−3z)(−2x)

=4x 2 +25y 2 +9z 2 −20xy−30yz+12zx.