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प्रश्न
Solve x2 + 7x = 7 and give your answer correct to two decimal places
उत्तर
Given quadratic equation is x2 + 7x = 7
`=> x^2 + 7x - 7 = 0`
Comparing with `ax^2 + bx +c =0` we have a = 1, b = 7 and c = -7
`x = (-b+-sqrt(b^2 -4ac))/(2a) `
`=> x = (-7 +- sqrt(7^2 - 4 xx 1 xx (-7)))/(2 xx1)`
`=> x = (-7+- sqrt77)/2`
`=> x = (-7+- 8.77)/2`
`=> x = (-7+8.77)/2` and `x = (-7-8.77)/2`
`=> x = 1.77/2` and `x = (-15.77)/2`
`=> x = 0.885 and x = -7.885`
=> x = 0.89 and x = -7.89 (correct to two decimal places)
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