Mathematics
If the roots of x2 - px + 4 = 0 are equal, the value (values) of p is/are :
4 and -4
4
-4
4 or -4
Answer
Comparing equation x2 - px + 4 = 0, with ax2 + bx + c = 0, we get :
a = 1, b = -p and c = 4.
Since, roots are equal.
∴ D = 0
∴ b2 - 4ac = 0
⇒ (-p)2 - 4 × 1 × 4 = 0
⇒ p2 - 16 = 0
⇒ p2 - 42 = 0
⇒ (p - 4)(p + 4) = 0
⇒ (p - 4) = 0 or (p + 4) = 0
⇒ p = 4 or p = -4.
Hence, Option 4 is the correct option.
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