Question

Which question shows the quadratic fomula used correctly to solve 7x^2=9+x for x

Answer 1

x =
`\frac{-b\pm\sqrt{b^(2)-4ac} }{2a}`

Explanation:

We have

7x²=9+x

Subtracting x from both sides, we get

7x²-x=9+x-x

Cancelling out +x and -x from the right side, we get

7x²-x=9

Subtracting 9 from both sides, we get

7x²-x-9=9-9

Cancelling out 9 and -9 from the right side, we have

7x²-x-9 = 0

The above equation is in the form ax²+bx+c=0 where upon comparing we get a= 7 , b = -1 and c= -9

We can solve for x using the below quadratic formula:-

x =
`\frac{-b\pm\sqrt{b^(2)-4ac} }{2a}`

Upon solving we'll get two values for x, one positive an the other negative.