Multiply: (x10 9)(x10 - 9)
By difference of two squares:(x - y)(x +y) = x²- y²(x¹⁰ + y¹⁰)(x¹⁰ - y¹⁰)= (x¹⁰)² - (y¹⁰)² = x⁽² ˣ¹⁰⁾ - y⁽² ˣ¹⁰⁾ = x²⁰ - y²⁰ (x¹⁰ + y¹⁰)(x¹⁰ - y¹⁰) = x²⁰ - y²⁰ Hope this helps.
