Question

find the whole number such that four times the number subtracted from 3 times the square of the number makes 15

Answer 1

Let the number be x
Now According to Question
four times the number subtracted from 3 times the square of the number makes 15
= 3x²-4x= 15
D = b²-4ac
= 16-4(3)(-15)
= 16+180
= 196
Now
Roots are -b±√D/2a
= 4±14/6
= 3,-5/3
Here -5/3 is an integer thus the whole number will be 3

Hope it will help you

Answer 2

Let x = the number
then
3x^2 - 4x = 15
3x^2 - 4x - 15 = 0
replace -4x with:
3x^2 - 9x + 5x - 15 = 0
group terms:
(3x^2 - 9x) + (5x - 15) = 0
factor:
3x(x - 3) + 5(x - 3) = 0
(x - 3)(3x + 5) = 0
x = {3, -5/3}
throw out the fraction since we're looking for whole numbers
x = 3 
Answer by oberobic(2304)   (Show Source): You can put this solution on YOUR website!
x = a number
.
Three times the square of the number minus four times the number = 15.
3*x^2 - 4x = 15
3x^2 -4x -15 = 0
.
factor
(3x +5)(x -3) = 3x^2 -9x +5x -15 = 3x^2 -4x -15
.
x = -5/3 or 3
.
Obviously, -5/3 is not a whole number, so x =3 is the proposed solution.
.
Check to see if it is correct.
.3x^2 = 3(9) = 27
4x = 12
27-12 = 15
Correct
.
Answer: The whole number is 3.
.
Done.