If x2 - 4x = 5, the value of x is :
5
-1
5 or -1
5 and -1
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Given,
⇒ x2 - 4x = 5
⇒ x2 - 4x - 5 = 0
⇒ x2 - 5x + x - 5 = 0
⇒ x(x - 5) + 1(x - 5) = 0
⇒ (x + 1)(x - 5) = 0
⇒ (x + 1) = 0 or (x - 5) = 0
⇒ x = -1 or x = 5.
Hence, Option 3 is the correct option.
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If 3x2 - kx - 15 = (3x - 5)(x + 3), the value of k is :
4
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3
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0
0 and 4
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