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Question
Solve the following equation for x and give, in the following case, your answer correct to 2 decimal places:
4x2 – 5x – 3 = 0
Solution
Given equation 4x2 – 5x – 3 = 0
Comparing with ax2 + bx + c = 0, we have
a = 4, b = – 5, c = – 3
∴ `x = (-b ± sqrt(b^2 - 4ac))/(2a)`
= `(-(-5) ± sqrt((-5)^2 - 4 xx 4 xx (-3)))/(2 xx 4)`
= `(5 ± sqrt(25 + 48))/(8)`
= `(5 ± sqrt(73))/(8)`
= `(5 ± 8.544)/(8)`
= `(5 + 8.544)/(8) or (5 - 8.544)/(8)`
= `(13.544)/(8) or (-3.544)/(8)`
= 1.693 or – 0.443
= 1.69 or – 0.44 ...(correct to 2 decimal places)
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