MCQ
$(1-2x)^{-2}$ ના વિસ્તાન્રમાં $x^7$ નો સહગુણક ...... છે.
- A1234
- B2345
- C4565
- ✓1024
$T_{r+1}=\frac{(-2)(-3)(-4)......(-2-r+1)}{r!}(-2x)^r$
$=\frac{(-1)^r(2)(3)(4)....(r+1)(-1)^r2^rx^r}{r!}$
$=\frac{(-1)^{2r}(r+1)r!2^r}{r!}x^r$
$(r+1)2^rx^r$
$r=7$લેતા, $T_8=(7+1)2^7x^7=8×128 x^7=1024x^7$
$x^7$ નો સહગુણક $=1024$
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