GMAT problems involving quadratic equations often require you to build a quadratic equation from factored form. Doing so is relatively easy using a simple multiplication process called FOIL, an acronym for the four steps of the process: First, Outer, Inside, Last.Let's change the expression (x+4)(x-5) into a quadratic expression using FOIL:First: multiply the first term of each factor together: x·x = x2Outer: Multiply the outer terms of the expressions together: x·(-5) = -5xInside: Multiply the inside terms of the expressions together: 4·x = 4xLast: Multiply the last term of each factor together: 4·(-5) = -20.Finally, add the 4 terms: x2 - 5x + 4x - 20. Combine the two middle terms to reach our quadratic expression x2 - x - 20.

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