Posted by Algebra Parent on Friday, March 21, 2008 at 7:20pm.
Can someone tell me if these problems have the right answers? I am tooooooo old to know this any more. I understand the first one, but 2&3 are vaguely familiar.
the answer is x=-1/2 +/- 1/10
#2 solve for V=1/3Bh for B
answer is B=V/ 1/3h
#3 Find equation of line (-4,-3) and (5,6)
answer is 1x+y=-4
Algebra - Reiny, Friday, March 21, 2008 at 7:38pm
the first one is wrong
25x^2+25x+6=0 factors to
(5x+2)(5x+3) = 0
so x = -2/5 or x = -3/5
in the second one
V=1/3Bh multiply both sides by 3
3V = Bh now divide both sides by h
3V/h = B
no for the third one, sorry 3 strikes!
most students appear to be taught the
y = mx + b method
so slope = m = 9/9 = 1
so y = x + b
sub in one of the points, say (5,6)
6 = 5 + b
b = 1
so the equation is y = x + 1 or
x - y = -1
(test the two given points, they both work. They don't work in your equation)
Algebra - Algebra Parent, Friday, March 21, 2008 at 7:56pm
#3 He has the m=9/9 slope
the 6 and 5 are written m=6-(-3)/5-(-4), so he has a - sign where there should be a plus sign? He must be using the wrong formula, because at the beginning he has m=y2-y1/x2-x1. The numbers 2&1 are below the y and x. Hehas used the formula y=mx+b before.
Algebra - Reiny, Friday, March 21, 2008 at 8:35pm
the slope is indeed 9/9 which is 1
the calculations for slope are correct, I don't like the way you typed them.
You have to use brackets to control the proper order of operation, so your
m=6-(-3)/5-(-4) should be written as
m=(6-(-3)) / (5-(-4))
m = (6+3) / (5+4) because 6 - (-3) = 6 + (3)
m = 9/9
m=y2-y1/x2-x1 is simply the formula used to find slope if you are given two points.
it means take (the y of the second point - the y of the first point), then divide it by (the x of the second point - the x of the first point)
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