每日一题

Mathematics>Standard Multiple Choice

Read the following SAT test question and then click on a button to select your answer.

First, 3 is subtracted from x and the square root of the difference is taken. Then, 5 is added to the result, giving a final result of 9. What is the value of x?

(A) 3
(B) 4
(C) 5
(D) 16
(E) 19

答案和解析

答案：E

解析：

When 3 is subtracted from x, the result is x-3. The square root of this difference is square root (x-3). When 5 is added to square root (x-3), the final result is 9. This can be written as (square root (x-3))+5 = 9. Subtracting 5 from both sides gives the equation square root (x-3) = 4. Squaring both sides of this equation gives x-3 = 16, or x = 19.