Question

Solve by completing the square; round to the nearest hundredth 3×2+15×=108?

Answer 1

4, or -9

Explanation:

To solve the equation of `3x^2 + 15x = 108`, rearrange this first so that all the numbers are on the left,
`3x^2 + 15x-108` = 0
Then make the coefficient of `x^2` to 1. (Divide by 3)
That will be `x^2+5x-36`.
The formula for completing the square is
`(a+b/2)^2-(b/2)^2+c`.
So `(x+5/2)^2-25/4-36`
Next, simplify the constant (numbers without x)
`-36-25/4` is `-169/4`
Bring this number to the right and square root it to get rid of the square on the left-hand side.
`(x+5/2)=√169/4^`
Solve to make x the subject.
`x=-5/2+√169/4`
or it can be `x=-5/2-√169/4`