Question

11. Solve by cross multiplication: x+y = a+b and ax-by= a^2- b^2.

Answer 1

Answer:→ x + y - (a + b) = 0

→ ax - by - (a² - b²) = 0

\mathsf{=  \frac{x}{ - ( {a}^{2}   -  {b}^{2})   - b(a + b)}}  \\  \mathsf{=  \frac{x}{ -  {a}^{2} +  {b}^{2}  - ab -  {b}^{2}  }} \\  \mathsf{= \frac{x}{ - a(a + b)}}  

\mathsf{ = \frac{ - y}{ - ( {a}^{2} -  {b}^{2} ) + a(a + b) }}  \\  \mathsf{=  \frac{ - y}{ -  {a}^{2} +  {b}^{2} + {a}^{2}  + ab }} \\  \mathsf{=  \frac{ - y}{b(a + b)}}

\mathsf{ = \frac{1}{ - b - a}}  \\ \mathsf{= \frac{1}{- (a + b)}}  

______________________________

\mathsf{\frac{x}{-a(a+b)} = \frac{-y}{b(a+b)} = \frac{1}{-(a + b)}} \\ \mathsf{x = \frac{-a(a+b)}{-(a+b)} = a} \\ \mathsf{-y = \frac{b(a+b)}{-(a+b)} = b}

x = a & y = b

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