1、GRE（ QUANTITATIVE）练习试卷 19及答案与解析 1 For x=4, 3x2-5x+9=_ 2 (5x3+3x-12)-(2x3-6x+17)=_ 3 (4x2+2x)(x-6)=_ 4 What are the solution sets for x2+2x-48? 5 (x-4) and (2x+3) are the solution sets for what equation? GRE（ QUANTITATIVE）练习试卷 19答案与解 析 1 【正确答案】 To solve the equation, substitute 4 for x: 3(42)-5(4)+9=
2、 3(16)-20+9= 48-20+9=37 2 【正确答案】 To add or subtract polynomials, combine like terms (remember to keep track of the negative signs!): (5x3+3x-12)-(2x3-6x+17) (5x3-2x3)+(3x+6x)-(17-12) 3x3+9x-5 3 【正确答案】 Use the Distributive Property to multiply each term of one polynomial by each term of the other (re
3、member to use the FOIL method). (4x2+2x)(x-6) First terms: (4x2)(x)=4x3 Outside terms: (4x2)(-6)=-24x2 Inside terms: (2x)(x)=2x2 Last terms: (2x)(-6)=-12x Now place the terms in decreasing order of the exponents: 4x3-22x2-12x 4 【正确答案】 Find two numbers whose product is -48 and sum is 2.8 and -6 are the only possible numbers. Therefore, the solution sets are (x-6) and (x+8). 5 【正确答案】 The solution sets are given, so multiply the two sets together to find the original equation, using the FOIL method: (x-4)(2x+3) =2x2+3x-8x-12 =2x2-5x-12
