Question

Which equation shows the quadratic formula used correctly to solve 7x2 = 9 + x for x?

Answer 1

The equation should be 7x^2 -x-9=0

Answer 2

The equation
`x=(-(-1)\pm √((-1)^2-4(7)(-9)))/(2(7))` shows the quadratic formula used correctly to solve the given equation.

Explanation:

If a quadratic equation is defined as
`ax^2+bx+c=0`, then the quadratic formula is

`x=(-b\pm √(b^2-4ac))/(2a)`

The given equation is

`7x^2=9+x`

Subtract 9 and x from both the sides.

`7x^2-x-9=0`

Here, a=7, b=-1 and c=-9.

Substitute a=7, b=-1 and c=-9 in the quadratic formula.

`x=(-(-1)\pm √((-1)^2-4(7)(-9)))/(2(7))`

Therefore the equation
`x=(-(-1)\pm √((-1)^2-4(7)(-9)))/(2(7))` shows the quadratic formula used correctly to solve the given equation.