How do you solve 3x^2 -12x = 93x212x=9 using the quadratic formula?

1 Answer
Apr 24, 2017

x=2+-sqrt7x=2±7

Explanation:

"rearrange terms and equate to zero"rearrange terms and equate to zero

rArr3x^2-12x-9=03x212x9=0

"divide all terms by 3"divide all terms by 3

rArrx^2-4x-3=0x24x3=0

"compare to standard form " ax^2+bx+c=0compare to standard form ax2+bx+c=0

"here " a=1,b=-4" and " c=-3here a=1,b=4 and c=3

"using the " color(blue)"quadratic formula"using the quadratic formula

color(red)(bar(ul(|color(white)(2/2)color(black)(x=(-b+-sqrt((b^2-4ac)))/(2a))color(white)(2/2)|)))

rArrx=(-(-4)+-sqrt((-4)^2-(4xx1xx-3)))/(2xx1)

color(white)(rArrx)=(4+-sqrt(16+12))/2=(4+-sqrt28)/2

color(white)(rArrx)=2+-1/2sqrt28

color(white)(rArrx)=2+-1/2sqrt(4xx7)

color(white)(rArrx)=2+-sqrt7