2a²b＋3a²b－1/2a²b ＝(2+3-1/2)a^2b = 4 1/2a^2b
a³＋a²b－ab²＋a²b－ab²＋b³= a^3 + 2a^2b -2ab^2 + b^3
2/3a²－1/2ab＋3/4a²＋ab－b²=(2/3 + 3/4)a^2 +(-1/2 +1)ab -b^2
= 17/12 a^2 +1/2 ab -b^2
= 1 5/12 a^2 + 1/2 ab -b^2
10a＋6a－7a＋3b－10a＋10b＋12a＋8b
= (10 +6 -7 -10 +12)a +(3 +10 + 8)b
= 11a + 21b
6x²y＋2xy－3x²y²－7x－5yx－4y²x²－6x²y
= (6-6)x^2y +(2-5)xy + (-3 -4)x^2y^2 - 7x
= -7x^2y^2 - 3xy - 7x