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Mathematics

Verify that x×(yz)=x×yx×zx \times (y - z) = x \times y - x \times z, if

x=34,y=89x = \dfrac{3}{4}, y = \dfrac{8}{9} and z=5z = -5

Rational Numbers

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Answer

To prove:

x×(yz)=x×yx×zx \times (y - z) = x \times y - x \times z

Taking LHS:

x×(yz)=34×(89(5))=34×(8951)x \times (y - z)\\[1em] =\dfrac{3}{4} \times \Big(\dfrac{8}{9} - (-5)\Big)\\[1em] =\dfrac{3}{4} \times \Big(\dfrac{8}{9} - \dfrac{-5}{1}\Big)

LCM of 9 and 1 is 3 x 3 = 9.

=34×(8×19×15×91×9)=34×(89459)=34×(8(45)9)=34×(8+459)=34×(539)=(3×534×9)=(15936)=(5312)=\dfrac{3}{4} \times \Big(\dfrac{8 \times 1}{9 \times 1} - \dfrac{-5 \times 9}{1 \times 9}\Big)\\[1em] =\dfrac{3}{4} \times \Big(\dfrac{8}{9} - \dfrac{-45}{9}\Big)\\[1em] =\dfrac{3}{4} \times \Big(\dfrac{8 - (-45)}{9}\Big)\\[1em] =\dfrac{3}{4} \times \Big(\dfrac{8 + 45}{9}\Big)\\[1em] =\dfrac{3}{4} \times \Big(\dfrac{53}{9}\Big)\\[1em] =\Big(\dfrac{3 \times 53}{4 \times 9}\Big)\\[1em] =\Big(\dfrac{159}{36}\Big)\\[1em] =\Big(\dfrac{53}{12}\Big)

Taking RHS:

x×yx×z=34×8934×5=3×84×93×54×1=2436154=23154x \times y - x \times z\\[1em] =\dfrac{3}{4} \times \dfrac{8}{9} - \dfrac{3}{4} \times -5\\[1em] = \dfrac{3 \times 8}{4 \times 9} - \dfrac{3 \times -5}{4 \times 1}\\[1em] =\dfrac{24}{36} - \dfrac{-15}{4}\\[1em] =\dfrac{2}{3} - \dfrac{-15}{4}

LCM of 3 and 4 is 2 x 2 x 3 = 12

=2×43×415×34×3=8124512=8(45)12=8+4512=5312=\dfrac{2 \times 4}{3 \times 4} - \dfrac{-15 \times 3}{4 \times 3}\\[1em] =\dfrac{8}{12} - \dfrac{-45}{12}\\[1em] =\dfrac{8 - (-45)}{12}\\[1em] =\dfrac{8 + 45}{12}\\[1em] =\dfrac{53}{12}

∴ LHS = RHS

x×(yz)=x×yx×zx \times (y - z) = x \times y - x \times z

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