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How do you “use the formula” to find the values of x correct to 2dp?

April 26, 2017Mathematics values

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How do you “use the formula” to find the values of x correct to 2dp?

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Use the quadratic equation formula… x = (–b +/– SqRt(b² – 4ac)) / 2a (or look here to see it written in a nicer way: http://www.purplemath.com/modules/quadfo… ) so work out the values of a, b, c and pop them in the formula. Starting with the first… 2x² + 9x – 12 = 0 a = 2 b = 9 c = –12 [–9 +/– SqRt(9² – (4 × 2 × –12))] / (2 × 2) = [–9 +/– SqRt(81 – (–96))] / 4 = [–9 +/– SqRt(177)] / 4 = [–9 +/– 13.3] / 4 = 1.076 or –5.576 = 1.08 or –5.58 to 2 d.p. x² + 4x – 13 = 0 a = 1 b = 4 c = –13 x = [–4 +/– SqRt(4² – (4 × 1 × –13)] / (2 × 1) = [–4 +/– SqRt(16 – – 52)] / 2 = [–4 +/– SqRt(68)] / 2 = [–4 +/– 8.246] / 2 = 2.123 or –6.123 = 2.12 or –6.12 to 2 d.p.