1) which method is most efficient method to use to solve 2x^2+4x-3=0

2) which method is most efficient method to use to solve x^2+5x-6=0

3) which method is most efficient method to use to solve 2x^2+4x-7=0

a. factoring
b. isolating the x^2 term and finding the square root of both sides
c. using the quadratic formula
d. all three methods would be

(the answer choices are the same for all the problems)