If x4 + 2x3 + ax2 + bx + 9 is a perfect square where a and b are positive real numbers, then the value of a and b is?
A. a = 5, b = 6
B. a = 6, b = 7
C. a = 7, b = 7
D. a = 7, b = 8
Answer: Option B
Solution(By Examveda Team)
$$\eqalign{ & {x^4} + 2{x^3} + a{x^2} + bx + 9 \cr & {\text{Put }}x = 1 \cr & = 1 + 2 \times 1 + a + b + 9 \cr & = 1 + 2 + a + b + 9 \cr & = 13 + a + b \cr} $$To make a perfect square numbers value of a + b must be either 3 or 13
Now, option (B) a = 6, b = 7
$$\eqalign{ & \therefore a + b = 13 \cr & {\text{make perfect square}} \cr & \left( {25 = {5^2}} \right) \cr} $$
Related Questions on Algebra
If $$p \times q = p + q + \frac{p}{q}{\text{,}}$$ then the value of 8 × 2 is?
A. 6
B. 10
C. 14
D. 16
A. $$1 + \frac{1}{{x + 4}}$$
B. x + 4
C. $$\frac{1}{x}$$
D. $$\frac{{x + 4}}{x}$$
A. $$\frac{{20}}{{27}}$$
B. $$\frac{{27}}{{20}}$$
C. $$\frac{6}{8}$$
D. $$\frac{8}{6}$$
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