Identify the roots of...

Question

Idnetify the roots of (x-3)(x+4)=18

 

A. -5 and 6

B. 3  and -4

C. -3 and 4

D. 5 and -6

Answer 1

Dil,

 

(x-3)(x+4)=18

x² + x - 12 = 18

x² + x - 12 -18 = 18 - 18

x² + x -30 = 0

x² + 6x - 5x -30 = 0

x(x + 6) - 5(x + 6) = 0

(x + 6)(x - 5) = 0

x = -6 or x = 5

Or, you could easily rule out B and C and try substituting -5. When that doesn't work, as it shouldn't, you would only have D for an answer.