লঘুমান গুরুমান বিষয়ক

ddx(ex2+xx2)\frac{d}{dx}(e^{x²} + x^{x²})

x(122x)2x(12-2x)² এর বৃহত্তম ও ক্ষুদ্রতম মান নির্ণয় করো

RUET 12-13

y=ex2+elnxx2=ex2+ex2lnxdydx=ex22x+ex2lnx(x21x+2xlnx) \mathrm{y}=\mathrm{e}^{\mathrm{x}^{2}}+\mathrm{e}^{\ln \mathrm{x}^{\mathrm{x}^{2}}}=\mathrm{e}^{\mathrm{x}^{2}}+\mathrm{e}^{\mathrm{x}^{2} \ln \mathrm{x}} \Rightarrow \frac{\mathrm{dy}}{\mathrm{dx}}=\mathrm{e}^{\mathrm{x}^{2}} \cdot 2 \mathrm{x}+\mathrm{e}^{\mathrm{x}^{2} \ln \mathrm{x}}\left(\mathrm{x}^{2} \cdot \frac{1}{\mathrm{x}}+2 \mathrm{x} \cdot \ln \mathrm{x}\right)

dydx=2xex2+xx2(x+2xlnx) \therefore \frac{\mathrm{dy}}{\mathrm{dx}}=2 \mathrm{xe}^{\mathrm{x}^{2}}+\mathrm{x}^{\mathrm{x}^{2}}(\mathrm{x}+2 \mathrm{x} \ln \mathrm{x}) Ans.

x(122x)2 \mathrm{x}(12-2 \mathrm{x})^{2} এর বৃহত্তম ও ক্ষুদ্রতম মান নির্ণয় কর।

Let, f(x)=x(122x)2=x(4x248x+144)=4x348x2+144x \mathrm{f}(\mathrm{x})=\mathrm{x}(12-2 \mathrm{x})^{2}=\mathrm{x}\left(4 \mathrm{x}^{2}-48 \mathrm{x}+144\right)=4 \mathrm{x}^{3}-48 \mathrm{x}^{2}+144 \mathrm{x} f(x)=12x296x+144;f(x)=24x96 f^{\prime}(x)=12 x^{2}-96 x+144 ; f^{\prime \prime}(x)=24 x-96

for minimum and maximum value

f(x)=12x296x+144=0x=6,2 \mathrm{f}^{\prime}(\mathrm{x})=12 \mathrm{x}^{2}-96 \mathrm{x}+144=0 \quad \therefore \mathrm{x}=6,2

f(2)=48<0 \mathrm{f}^{\prime \prime}(2)=-48<0 ; maximum value will be obtained. \quad \therefore maximum value f(2)=128 \mathrm{f}(2)=128

f(6)=48>0 \mathrm{f}^{\prime \prime}(6)=48>0 ; minimum value obtained.

\therefore minimum value f(6)=0 \mathrm{f}(6)=0

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