Question

Solve the following equation using quadratic formula: 

9x² + 7x – 2 = 0

Answer 1

Comparing equation 9x² + 7x – 2 = 0 with ax² + bx + c = 0, we get:

a = 9, b = 7 and c = –2

By formula,

`x = (-b ± sqrt(b^2 - 4ac))/(2a)`

Substituting values we get:

⇒ `x = (-(7) ± sqrt((7)^2 - 4 xx 9 xx (-2)))/(2(9))`

= `(-7 ± sqrt(49 + 72))/18`

⇒ `x = (-7 ± sqrt(121))/18`

= `(-7 ± 11)/18`

= `(-7 + 11)/8` or `(-7 - 11)/18`

= `4/18` or `(-18)/18`

= `2/9` or –1

Hence, `x = {2/9, -1}`.