If a + b = 10 and ab = 21, then the value of (a - b)2 is?
A. 15
B. 16
C. 17
D. 18
Answer: Option B
Solution(By Examveda Team)
$$\eqalign{ & a + b = 10{\text{ and }}ab = 21 \cr & \left( {a + b} \right) = 10 \cr & \Rightarrow {a^2} + {b^2} + 2ab = 100 \cr & \Rightarrow {a^2} + {b^2} = 100 - 2ab \cr & \Rightarrow {a^2} + {b^2} = 100 - 2 \times 21 \cr & \Rightarrow {a^2} + {b^2} = 100 - 42 \cr & {a^2} + {b^2} = 58\,.........(i) \cr & {\left( {a - b} \right)^2} = {a^2} + {b^2} - 2ab \cr & {\left( {a - b} \right)^2} = 58 - 2 \times 21 \cr & \left[ {{\text{from equation (i)}}} \right] \cr & = {\text{58}} - {\text{42}} \cr & {\left( {a - b} \right)^2} = 16 \cr} $$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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