Question

If x-y = 40 and x+y = 70, then what is the value of x squared -y squared ?

Answer 1

Let's see what to do buddy...

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Reminder:

$(a + b)(a - b) = {a}^{2} - {b}^{2}$

So we need to just Multiply above equations like this :

$x + y = 70$

$x - y = 40$

$(x + y)(x - y) = 70 \times 40$

${x}^{2} - {y}^{2} = 2800$

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And we're done.

Thanks for watching buddy good luck.

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