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Question
Solve the following equation for x and give, in the following case, your answer correct to 2 decimal places:
x2 – 3x – 9 = 0
Solution
x2 – 3x – 9 = 0
Here a = 1, b = –3 and c = –9
∴ `x = (-b +- sqrt(b^2 - 4ac))/(2a)`
= `(-(-3) +- sqrt((-3)^2 - 4(1)(-9)))/(2(1))`
= `(3 +- sqrt45)/2`
= `(3 +- 6.70)/2`
= `(3 + 6.70)/2` and `(3 - 6.70)/2`
= 4.85 and –1.85
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