0.5x2 + 0.4x2 - 0.2x2
Notice that all three term share a common factor, that being x2 . Factoring out x2 from all three terms, we arrive at the following:
x2(0.5 + 0.4 - 0.2) = x2(0.7) = 0.7x2
Likewise, since all three terms have a common base (x2) they are like terms and can thus be combined. That is, we can simply combine the coefficients of each term and keep the common base.