The roots of the equation (3−x)4+(2−x)4=(5−2x)4 are
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a
all real
b
all imaginary
c
two real and two imaginary
d
none of the above
answer is C.
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Detailed Solution
The given equation is (3−x)4+(2−x)4=(5−2x)4 ……(i) Put 3−x=a and 2−x=b Eq. (i) be comes a4+b4=(a+b)4 ⇒a4+b4=a4+b4+4a3b+6a2b2+4ab3 ⇒ 2ab(2a2+3ab+2b2)=0 ∴ a=0⇒3−x=0⇒x=3 b=0⇒2−x=0 ⇒ x=2 and 2a2+3ab+2b2=0 2(ab)2+3(ab)+2=0 ab=−3±9−164 3−x2−x=−3±i74 ⇒ 3−x2−x−1=−7±i74 ⇒ 12−x=−7±i74 2−x=4−7±i7 x−2=4−7±i7 x=−18±2i7−7±i7 Taking ‘+’ sign x=(−18+2i7)(−7−i7)(−7+i7)(−7−i7) =140+4i756 ∴ x=35+i714 Taking ‘-‘ sign, x=35−i714 Hence, roots of Eq. (i) are 2,3,35±i714 i.e., Two real and two imaginary.