Quadratic equations with decimal values are more difficult to solve because the guessandcheck and box methods of factoring quadratic equations are much less intuitively easy for decimal values. Solve these equations by multiplying both sides of the equation by a multiple of ten to eliminate the decimals and using the quadratic formula to find both values of x.

Multiply both sides of the quadratic equation by the smallest multiple of ten that will convert each decimal in the equation into a whole number. For example, given the quadratic equation x^2  0.2x  1.2 = 0, multiply both sides of the equation by 10 to eliminate all decimals from the equation, yielding the equation 10x^2 + 2x  12 = 0.

Label the constants of the quadratic equation A, B and C based on the standard form for a quadratic equation: Ax^2 + Bx + C = 0. In the example equation 10x^2 + 2x  12 = 0, A = 10, B = 2 and C = 12.

Plug the values of A, B and C into the quadratic formula: x = (B +/ Sqrt(B^2  4AC)) / 2A. In the above example, plug the values A = 10, B = 2 and C = 12 into the formula to get the equation x = (2 +/ Sqrt(2^2  4(10)(12))) / 2*10.

Solve for first value of x by simplifying the right side of the equation with a positive square root. In the above example, the equation simplifies to x = (2 + Sqrt(484)) / 20, or x = 1.

Solve for the second value of x by simplifying the left side of the equation with a negative square root. In the above example, the equation simplifies to x = (2  Sqrt(484)) / 20, or x = 6/5. The two solutions to the quadratic equation are therefore x = 1 and x = 6/5.
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