Solve the equation in the real number system: 2x^3+x^2-7x-6=0 (MULTIPLE CHOICE)

Question

Solve the equation in the real number system: 2x³+x²-7x-6=0 

 

a. x=-3/2, -1, 2

b. x=-1, 2

c. x=-2, -1, 2

d. -3, -1, 2

Answer 1

The great thing about multiple choice is you can use their answer candidates to find the answer.

you can see that all answer candidates have -1, 2. so you can divide (x+1)or (x-2) into the cubic equation to get

a quadradic, then solve quadratic by additional division of the other factor or Q. formula.

 

2x^3  + x^2 - 7x -6 = 0

 

divide by x+1 gives 2x^2  - x - 6

factor out x-2 gives (2x + 3)

roots are -3/2, -1, 2