Math

Question

12x² + 7x = 10
Please solve using the quadratic formula.

2 Answer

  • 12x² + 7x - 10 = 0

    Quadratic Formula = D = b² - 4ac

    = (7)² - 4(12)(-10)
    = 49 + 480
    = 529

    Now 
     x = - b + √D   , x = -b - √D
              2a                   2a

    x = -7 + 23      , x = -7 - 23
             24                     24

    x = 16/24        , x = -30/24

    x = 2/3            , x = -5/4
  • 12x²+7x=10
    or,12x²+7x-10
    As the equation is of the form +,+,-,find mentally 2 numbers whose sum is +7 and product is 12*(-10)=-120.One number will be positive and the other negative such that +ve no. > -ve no. (As their sum is a postive number)Such numbers are +15 and -8.
    Therefore,the equation can be written as:
    12x²+15x-8x-10
    factorizing the (1st and 2nd ) and (3rd and 4th) terms together,we get
    3x(4x+5)-2(4x+5)
    or,(3x-2)(4x+5)=0
    Either 3x-2=0 or 4x+5=0
    Either 3x=2 or 4x=-5
    Either x=2/3 or x=-5/4
    Ans:The 2 roots of the equation are: x=2/3 or -5/4.