Asked by mathlab

Solve for x in the equation (x − 7)^2 − 4 = (x + 1)^2.

Answered by Reiny
(x − 7)^2 − 4 = (x + 1)^2
x^2 - 14x + 49 - 4 = x^2 + 2x + 1
-16x = -44
x = 44/16 = 11/4 or 2.75
Answered by mathlab
follow up quesiton

11/4 or 2.75

how do u convert this without using calculator?
Answered by Reiny
to divide by 4 in my head,
I take half of my number and then I take another half

(little tricks that old people still know and use)

so half of 11 is 5.5 and half of 5.5 is 2.75
Think of money, half of $5.50
half of $5 is 2.50, and half of 50 cents is 25 cents
what is 2.50 + 25 cents ?
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