guide 2, page 179, if g(x) = 3x +

[abhisheks901]

if g(x) = 3x + (x)^ (1/2), what is the value of g(d^2 +6d+9) ? algebra, guide 2, page 179, que. 7, 6th edition


in solution to the above que, when we did square root of d^2+6d+9, it gave two answers : +(d+3) and -(d+3).

whereas, it is clearly mentioned on page 71 of algebra guide 2,6th edition, chapter 5 that " if a given equation contains a square root symbol on the GMAT, only use the positive root.

please solve

thanks

[Sage Pearce-Higgins]

Good point. There are two sides to this argument. On one hand, the square root is given to us in the formula, so we should only consider the positive root. But on the other hand, we've formed the equation by substituting the expression into the formula, so the equation wasn't technically "given" and we should consider both roots.

Actually, I wouldn't worry about this. GMAT is really good in official problems at avoiding confusion. I had a brief look in my Official Guide for any comparable problems but I couldn't find any. Let me know if you do. In any case I've never seen a problem that you'd get wrong by considering negative square roots.

Finally, this problem is designed to be a supplementary problem to help you on your algebra. There's no harm in considering the negative square root even though I'm inclined to agree with you that it's unnecessary for us to include that part in the explanation.