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# Algebra question!!?

What three techniques can be used to solve a quadratic equation? Demonstrate these techniques on the equation "12x2 - 10x - 42 = 0."

THANK YOU!!!!!!

### 5 Answers

- 1 decade agoFavorite Answer
the third way is completing the square:

12x^2 - 10x = 42,

so

x^2 - 5/6 x = 42/12 = 21/6

cut the 5/6 in half to get 5/12, and add (5/12)^2 to both sides.

x^2 - 5/6 x + 25/144 = 21/6 + 25/144

The left side collapses into

(x - 5/12)^2, and 7/6 + 25/144 = (584 + 25)/144 = 529/144

so

(x - 5/12)^2 = 529/144

x - 5/12 = +/- sqrt(529/144) = +/- 23/12

x= 5/12 + 23/12 = 28/12 = 7/3 or x = 5/12 - 23/12 = -18/12 = -3/2.

- 1 decade ago
"12x2 - 10x - 42 = 0."

Technique one: factoring...

Technique two: the quadratic equation

Technique three: Simplifying the equation first (a 2 can be divided out before you continue)

- 1 decade ago
well theres factoring, like (6x -4)(2x+12)=0

andd quadratic equation; -b + or - the square root of the quantity b(squared) -4ac all over 2a

idk what the 3rd is;; substitution or synthetic division?

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