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Question
Solve the following equation by using formula :
x2 + 7x – 7 = 0
Solution
x2 + 7x – 7 = 0
Here a = 1, b = 7, c = -7
∴ D = b2 - 4ac
= (7)2 - 4 x 1(-7)
= 49 + 28
= 77
∵ x = `(-b ± sqrt("D"))/(2a)`
= `(-7 ± sqrt(77))/(2 xx 1)`
= `(-7 ± sqrt(77))/(2)`
∴ `x_1 = (-7 + sqrt(77))/(2) and x_2 = (-7 - sqrt(77))/(2)`
Hence x = `(-7 + sqrt(77))/(2), (-7 - sqrt(77))/(2)`.
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