ALGEBRA 1

If x²  - y² = 700 and x + y = 7, find the value of x-y.

solution

x²  - y² = 700

From difference of two squares;

           a² - b² = (a - b)(a + b)

x²  - y² = 700

(x - y)(x + y) = 700

(x - y) x 7 = 700

7(x - y) = 700

7(x - y) = 700

7              7

(x - y) = 100

x - y = 100    answer

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NECTA FORM II - 2013 QN. 10

If x²  - y² = 10 and x + y = 2, find the value of x-y