Posted by mathlab on Thursday, March 14, 2013 at 7:34pm.
Solve for x in the equation (x − 7)^2 − 4 = (x + 1)^2.

math  Reiny, Thursday, March 14, 2013 at 7:51pm
(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

math  mathlab, Thursday, March 14, 2013 at 7:54pm
follow up quesiton
11/4 or 2.75
how do u convert this without using calculator?

math  Reiny, Thursday, March 14, 2013 at 8:01pm
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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