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Mathematics

Given log10 x = 2a and log10 y = b2\dfrac{b}{2} .

(i) Write 10a in terms of x .

(ii) Write 102b+1 in terms of y .

(iii) If log10 P = 3a - 2b, express P in terms of x and y.

Logarithms

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Answer

(i) Given: log10 x = 2a

102a10^{2a} = x

(10a)2(10^a)^2 = x

10a=x10^a = \sqrt{x}

Hence, the value of 10a=x10^a = \sqrt{x}.

(ii) Given, log10 y = b2\dfrac{b}{2}

10b210^{\dfrac{b}{2}} = y

Squaring both sides, we get:

10b=y210^{b} = y^2

Again squaring both sides, we get:

102b=y410^{2b} = y^4

Multiplying both sides by 10,

102b×10=y4×1010^{2b} \times 10 = y^4 \times 10

102b+1=10y410^{2b + 1} = 10y^4

Hence, the value of 102b+1=10y410^{2b + 1} = 10y^4.

(iii) Given: log10 P = 3a - 2b

⇒ P = 103a2b10^{3a - 2b}

⇒ P = 103a÷102b10^{3a} \div 10^{2b}

⇒ P = (x)3÷y4(\sqrt{x})^3 \div y^4

⇒ P = (x)32÷y4(x)^{\dfrac{3}{2}} \div y^4

⇒ P = x32y4\dfrac{x^{\dfrac{3}{2}}}{y^4}

Hence, the value of P = x32y4\dfrac{x^{\dfrac{3}{2}}}{y^4}.

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