(2x² +3x -4) + (8 -3x) + (-5x² +2)
= x²(2 -5) +x(3 -3) +(-4 +8 +2)
= -3x² +6
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The process here is called "collecting terms", which means you add the coefficients of "like" terms. Terms are "like terms" when they have the same constellation of variables. Here, there are three different kinds of like terms:
• x² terms
• x terms
• constants
This process is an application of the distributive property, as you can see on the second line of the solution above.