Question

x+y =1 and x-y=7 find the value of a) 5(x^2 +y^2) b) xy​

Answer 1

Step-by-step explanation:

$x + y = 1........equ .\: (1)$

$x - y = 7..........equ .\: (2)$

Adding equation 1 and 2, we get,

$x + y + x - y = 1 + 7$

$2x = 8 \\ \\ x = \frac{8}{2} = 4$

Substituting value of x in equation 1, we get,

$4 + y = 1 \\ \\ = > y = 1 - 4 \\ \\ = > y = - 3$

So substituting value of x and y in a), we get,

$5( {4}^{2} + { - 3}^{2} ) \\ \\ = > 5(16 + 9) = 5(25) \\ \\ = > 125$

Substituting value of x and y in b), we get,

$(4)( - 3) = - 12$

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