Question

If 4 is a solution to x^2+bx-12=0, then b=?

Answer 1

b = -1

Explanation:

First plug in 4 for each x:

`x^2+bx-12=0\\(4)^2+b(4)-12=0`

Then simplify by multiplying out what you can with 4:

`(4)^2+b(4)-12=0\\16+4b-12=0`

After simplify further by combining like terms:

`16+4b-12=0\\4b +4=0`

Then isolate b on one side by subtracting 4 from each side:

`4b+4=0\\(-4)+4b+4=0+(-4)\\4b=-4`

Finally isolate b further by dividing each side by 4 to get b alone and find the answer:

`4b=-4\\(4b)/(4)=(-4)/(4) \\ b=-1`