Question

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Solve the following system of equations using cross multiplication method

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Ans in book: x=3 , y=2

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Answer 1

Answer:

33/13, 30/13

Step-by-step explanation:

Given Equation is 2x + 3y - 12 = 0  ---- (i)

Given Equation is -7x + 9y - 3 = 0  ----- (ii)

Here,

a₁ = 2, b₁ = 3, c₁ = -12.

a₂ = -7, b₂ = 9, c₂ = -3

Cross-multiplication method:

x/(b₁c₂ - b₂c₁) = y/c₁a₂ - c₂a₁) = 1/(a₁b₂ - a₂b₁)

(i)

x/(b₁c₂ - b₂c₁) = 1/(a₁b₂ - a₂b₁)

⇒ x/(3)(-3) - (9)(-12) = 1/(2)(9) - (-7)(3)

⇒ x/99 = 1/39

⇒ x = 33/13.

(ii)

y/(c₁a₂ - c₂a₁) = 1/(a₁b₂ - a₂b₁)

⇒ y/(-12)(-7) - (-3)(2) = 1/(2)(9) - (-7)(3)

⇒ y/90 = 1/39

⇒ y = 30/39.

Note: Your answers are wrong!

Hope it helps!

Answer 2

Step-by-step explanation:

Given Equation is 2x + 3y - 12 = 0  

Given Equation is -7x + 9y - 3 = 0  

Here,

a₁ = 2, b₁ = 3, c₁ = -12.

a₂ = -7, b₂ = 9, c₂ = -3

x/(b₁c₂ - b₂c₁) = y/c₁a₂ - c₂a₁) = 1/(a₁b₂ - a₂b₁)

x/(b₁c₂ - b₂c₁) = 1/(a₁b₂ - a₂b₁)

x/(3)(-3) - (9)(-12) = 1/(2)(9) - (-7)(3)

x/99 = 1/39

x = 33/13.

y/(c₁a₂ - c₂a₁) = 1/(a₁b₂ - a₂b₁)

y/(-12)(-7) - (-3)(2) = 1/(2)(9) - (-7)(3)

y/90 = 1/39

y = 30/39.