返回列表 发帖

GMAT Tip: Wacky Roots, continued…

In our last post we promised to review some tough roots and radicals questions incorporating the top tips we provided last week. We’ll keep this post simple by working through a common but complex GMAT questions that focus on radicals and roots. Can you figure out how you would identify the easiest way to get started on these questions? How would you apply our top four tips?

Question #1


The first step to this question is to square both sides to get rid of the radical on the left-hand side:

(square root of 3 – x)^2 = (square root of x + 3)^2

3 – x = x + 3(square root of x) + 3(square root of x) + 9


HINT: Many test takers fail to recognize that you need to FOIL out the right-hand side of the equation, rather than the correct answer being x + 9.

Continue to further simplify to find that:

3 – x = x + 2(3(square root of x) + 9

3 – x = x + 6(square root of x) + 9

0 = 2x + 6(square root of x) + 6

0 = 2(x + 3(square root of x) + 3)


We no longer worry about the 2 coefficient, so we just repeat the steps that we used in the beginning to remove one more square root by squaring both sides.

0 = x + 3(square root of x) + 3

-3(square root of x) = x + 3

(-3(square root of x))^2 = (x+3)^2

9x = x^2 + 6x + 9

0 = x^2 – 3x + 9


Here, we would find that this question is impossible to factor into two different roots, so hopefully you’ve remembered that you don’t need to know the quadratic equation for the GMAT exam and re-read the question to find out that we are actually solving for x^2 and not x!


Additionally, fingers crossed you’ve taken a quick gander through the answer choices and realized that it is totally possible that the answer choice could have a variable, and by rearranging the equation we find that –

-x^2 = -3x + 9

x^2 = 3x – 9

Making the answer choice (E).


Wait, so how did we use those four tips again? Trick question – this question doesn’t necessarily incorporate the tips from last week. We hate to keep harping on it, but the ultimate key to success on the GMAT is having a flexible thinking mindset. What’s the quickest way to solve a question in under two minutes? Having a full toolkit, and practice, and helps you manipulate questions to the quickest but correct answer. Plus, never giving up.

收藏 分享
[img][/img]

谢谢楼主的分享...

TOP

Mark一下!!!

TOP

顶顶顶顶顶

TOP

~\(≧▽≦)/~

TOP

thanks!!!

TOP

赞赞赞赞赞

TOP

thanks...

TOP

Mark一下!!!

TOP

thanks...

TOP

返回列表

站长推荐 关闭


美国top10 MBA VIP申请服务

自2003年开始提供 MBA 申请服务以来,保持着90% 以上的成功率,其中Top10 MBA服务成功率更是高达95%


查看