Answers

2015-01-31T19:23:30+05:30
6b²+(-9b²)+12b²+20b²=35b²..............................if addition
6b²-(-9b²)-12b²-20b²=6b²+9b²-22b²=15b²-22b²=-7b².............if subtraction
6b²*-9b²*12b²*20b²=-12960b⁴..............if multiplication
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