巍哥数学-录播课GRE数学第二章.pptVIP

练习：求抛物线2x2-5x+7=0的顶点，x轴的交点，y轴的交点。 * 例1： y=2x2+7x-3 Quantity A Quantity B x y A. Quantity A is greater. B. Quantity B is greater. C. The two quantities are equal. D. The relationship cannot be determined from the information given. * 2) 圆 考点：根据已知条件求出圆的解析方程。 圆心为(a, b)，半径为r的圆的解析方程为： (x-a)2+(y-b)2=r2 练习：求以(3, 4)为圆心，半径为5的圆的解析方程。该圆是否过圆心？ * * * 例3：If 14x2-11x-15=0, then x2+2x+1= Indicate all such answers. A. 4/49 B. 8/81 C. 25/4 D. 9 E. 49/9 * 第四节 不等式 inequality 不等式 solution set 解集 equivalent inequality 等价不等式 考点：解不等式 1) 不等式两边同时加上或者减去一个数，不等式方向不改变； 2) 不等式两边同时乘以或者除以一个整数，不等式方向不改变； 3) 不等式两遍同时乘以或者除以一个负数，不等式方向改变； * 练习1：解不等式 3x+7>2x-4 * 练习2：解不等式 0.2x+3<0.1x-7 * 练习3：解不等式 0.2x-5≤0.4x+9 * 例1：If x<y<0, which of the following inequalities must be true? A. y+1<x B. y-1<x C. xy2<x D. xy<y2 E. xy<x2 * 第五节 函数 function 函数 operation 运算 domain 定义域 range 值域 考点： 1) 新定义函数的运算 2) 函数带入求值 * 例1：The figure above shows the graph of the function f in the xy-plane. What it the value of f(f(-1))? A. -2 B. -1 C. 0 D. 1 E. 2 * 例2: The operation ※ is defined for all integers x and y as x※y=xy-y. If x and y are positive integers, which of the following CANNOT be zero? A. x※y B. y※x C. (x-1) ※y D. (x+1) ※y E. x※(y-1) * 例3: Alice earns d dollars and has t percent of what she earns deducted for taxes. How much of what she earns does Alice have left after taxes? A. d(1-100t) dollars B. d(1-10t) dollars C. d(1-t) dollars D. d(1-0.1t) dollars E. d(1-0.01t) dollars * 第六节 应用题 Application 考点：把题干描述信息转化成数学表达形式（代数式，函数等） * 练习1：If the square of the number x is multiplied by 3, and then 10 is added to that product, the result can be represented by _____. 练习2：If John’s present salary s is increased by 14 percent, then his new salary is _____. 练习3：If y gallons of syrup