if one zero of the polynomial X square + bx + c is double The Other prove that 2 b square is equal to 9 a c
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CORRECT QUESTION:
If one zero of the polynomial ax² + bx + c is double the other . Then prove that 2b² = 9ac
ANSWER:
Given polynomial
x² + bx + c
Let α , β be the roots of the given polynomial
ax² + bx + c
★ We know that :
Sum of roots = -b/a
Product of roots = c/a
♦ Given condition:
- One root is double the other
- α = 2β
Roots are α , 2α
.°. α + 2α = - b/a
α.2α = c/a
→ 3α = - b/a
α = - b/3a
Assuming as equation (1)
→ 2α² = c/a
α² = c/2a
(-b/3a)² = c/2a. [ Using equation (1)]
b²/9a² = c/2a
b²/9a = c/2
2b² = 9ac
Hence, proved
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