trung bình hàng ngày của 50 đơn vị trong những ngày n qua tăng trung bình hàng ngày bao gồm cả ngày hôm nay của 90 đơn vị Nhân tử số và mẫu số bên trong dấu ngoặc đơn bởi x để loại bỏ các phân số hợp chất. | The Official Guide for GMAT Review 12th Edition 50 x n 55 _ x 90 n 1 daily average of 50 units over the past n days increased daily average when including today s 90 units Solving the first equation for x gives x 50n. Then substituting 50n for x in the second equation gives the following that can be solved for n Multiply the numerator and denominator inside the parentheses by x to eliminate the compound fractions. Distribute the x s. 1 x J2 1 - x 50n 90 n 1 55 n 1 50n 90 55n 55 50n 90 5n 35 n 7 multiply both sides by n 1 distribute the 55 subtract 50n and 55 from both sides divide both sides by 5 Since this is not one of the answer choices it is necessary to simplify further. With the knowledge that 1 x x 1 and 1 - x - x - 1 it can be stated that because the negative when squared is positive. The correct answer is E. The correct answer is A. 208. f x 1Ĩ I x -1 If x 0 and x 1 and if x is replaced by everywhere x in the expression above then the resulting expression is equivalent to A B C f x 1Ĩ I x -1 f x -1 J2 I x 1 x2 1 1 - x2 209. In the figure above if z 50 then x y D E x2 -1 x2 1 f x - 1 f 1 x 1 Algebra Simplifying algebraic expressions Substitute for x in the expression and simplify. A 230 B 250 C 260 D 270 E 290 Geometry Angles Measures of angles Refer to the figure below. 1 1J 1 x -1 7 254 Problem Solving Answer Explanations Triangle ABC is a right triangle and segment AB is parallel to segment ED since they are both perpendicular to the same segment BC . Therefore mEDEC mEBAC z 50 . So since EDEC and EAED form a straight line at E y 50 180 or y 130. The measure of an exterior angle of a triangle is the sum of the measures of the nonadjacent interior angles. Thus mEx mEz 90 or mEx 50 90 140 Thus x y 140 130 270. The correct answer is D. Geometry Simple coordinate geometry The line is shown going through the points 0 2 and 3 0 . The slope of the line can be found with the formula slope chlnge in y change in X x2 X1 for two points x1 y1 and x2 y2 . Thus .
