Question

Which constant must be added and subtracted to solve the quadratic equation 9x2 3/4x– 2 = 0 by the method of completing the square?(A) 1/8 (B) 1/64 (C) 1/4 (D) 9/64NCERT Class XMathematics - Exemplar ProblemsChapter _QUADRATIC EQUATIONS

Answer 1

9x^2 + 3/4x - 2 = 0

=> ( 3x )^2 + (3x)*1/4 - 2 = 0

=> ( 3x )^2 + 2 * ( 3x ) * 1/8 - 2 = 0

=> ( 3x )^2 + 1/64 + 2*(3x)*1/8 - 2 - 1/64 = 0

( add and subtract 1/64 )

=> { 3x + 1/8 }^2 = 2 + 1/64 = 129/64

thus 1/64 must be added .