if the answer of the sum for some quadratic polynomial is 2/3 can it be written as -(-2)/3 as it is mentioned to be -b/a (can we write like this in the exams if its correct) 

Asked by ravikaartik | 11th Jun, 2015, 05:35: PM

Expert Answer:

For a quadratic equation ax2+bx+c=0, the sum of the roots is -b/a
So the final result of sum depends on the sign of 'a' and 'b'.
For example, if the quadratic equation is 2x2+3x+5=0, the sum of the roots is -3/2. (negative)
                  if the quadratic equation is 2x2-3x+5=0, the sum of the roots is -(-3)/2= 3/2. (positive)
So, the sum of the roots depend on the signs of 'a' and 'b'. 
But if the result is 2/3, you dont have to write it as -(-2)/3. Simply divide 'b' by 'a' and put a negative sign. That gives you the sum of the roots of any quadratic.
Hope this helps.

Answered by satyajit samal | 12th Jun, 2015, 09:30: AM