RRB Group-D Model Paper 18 with answers for online practice

Given: One root of the equation is $5-2\sqrt{5}$ Concept: If one root of the quadratic equation is in this form ( $a+\sqrt{b}$ ) then the other roots must be conjugate ( $a-\sqrt{b}$ ) and vice-versa. Quadratic equation: $x^2$ - (sum of root) + (product of root) = 0 Calculation: Let α = $5-2\sqrt{5}$ and β = $5+2\sqrt{5}$ sum of root = α + β = $5-2\sqrt{5}+5+2\sqrt{5}$ =10 Product of root = α β = $(5-2\sqrt{5})(5+2\sqrt{5})$ = 25 - 20 = 5 Now, Quadratic equation = $x^2$ - 10x + 5 = 0 Hence, required quadratic equation is $x^2$ - 10x + 5 = 0