Use the identity a I a 2a 1 to calculate 4 l and 91 Show

Use the identity (a + I): = a, + 2a + 1 to calculate 4 l, and 91. Show your work. 4.

Solution

(40 + 1)^2 = 40^2 + 2(40)(1) + (1)^2

= 1600 + 80 + 1

= 1681

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(90 + 1)^2 = (90)^2 + 2(90)(1) + (1)^2

= 8100 + 180 + 1

= 8281