Question

For items 4 to 5, refer to the given problem below:
If 12 is subtracted from 3 times the square of a positive number the result is 5 times the number. What is the original number?
4. Which of the following equations would best represent the problem?
A. 3x2 - 12 = -5x
C. 3x2 - 12 = 5x
B. 12 - 3x2 = -5x
D. 12 - 3x2 = 5x
5. What is the original number?
A 3
C. 5
B. 4
D. 6​​

Answer 1

Answer:

4. C. 3x² - 12 = 5x

5. A. 3

Solution:

4.

Let the original number be x.

12 subtracted from ( 3 times the square of a positive number ) would be 3x² - 12

5 times the number is 5x

Therefore the answer for number 4 is C, 3x² - 12 = 5x

5.

The option 5 can be excluded as 12 is not a multiple of 5.

if x is 3:

3 × 9 - 12 = 5 × 3

15 = 15, which is true

If x is 4:

3 × 16 - 12 = 5 × 4

36 = 20, which isn't true.

if x is 6:

3 × 36 - 12 = 5 × 6

96 = 30, which also isn't true.

So the answer for number 5 is A, 3