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If 2x2 - 7x + 5 = 0, then what is the value of $${x^2} + \frac{{25}}{{4{x^2}}}?$$
Answer & Solution
Correct Answer:
Option
B
$$\eqalign{
& 2{x^2} - 7x + 5 = 0 \cr
& 2x + \frac{5}{x} = 7 \cr
& x + \frac{5}{{2x}} = \frac{7}{2} \cr
& {\left( {x + \frac{5}{{2x}}} \right)^2} = {\left( {\frac{7}{2}} \right)^2} \cr
& {x^2} + \frac{{25}}{{4{x^2}}} + 2 \times x \times \frac{5}{{2x}} = \frac{{49}}{4} \cr
& {x^2} + \frac{{25}}{{4{x^2}}} = \frac{{49}}{4} - 5 \cr
& {x^2} + \frac{{25}}{{4{x^2}}} = \frac{{29}}{4} \cr
& {x^2} + \frac{{25}}{{4{x^2}}} = 7\frac{1}{4} \cr} $$
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