Which constant must be added and subtracted to solve the quadratic equation `9x^2+ 3/4x - sqrt2 = 0` by the method of completing the square?

Options

A. `1/8`
B. `1/64`
C. `1/4`
D. `9/64`

Answer

B

Explanation

Given equation is `9x^(2)+3/4x-sqrt(2)=0`
`(3x)^(2)+1/4(3x)-sqrt(2)=0`
On putting `3x=y` we have `y^(2)+1/4y-sqrt(2)=0`
`y^(2)+1/4y+(1/8)^(2)-(1/8)^(2)-sqrt(2)=0`
`(y+1/8)^(2)=1/64+sqrt(2)`
`(y+1/8)^(2)=(1+64sqrt(2))/64`
Thus `1/64` must be added and substracted to solve the given equation.