I think B gives the best estimate and exact product because
1). 5.9 x 8.28 is very similar to 6 x 8 which equals 48.
and
2. 5.9 x 8.28 = 48.852.
Hopefully that made sense. :)
Just sub in ANY number for x and solve for y
5x + 7y = 19.....lets say x = 0
5(0) + 7y = 19
7y = 19
y = 19/7...so when x = 0, y = 19/7.....(0,19/7)
5x + 7y = 19....lets say x = 1
5(1) + 7y = 19
5 + 7y = 19
7y = 19 - 5
7y = 14
y = 14/7
y = 2.....so when x = 1, y = 2......(1,2)
5x + 7y = 19.....lets say x = 3
5(3) + 7y = 19
15 + 7y = 19
7y = 19 - 15
7y = 4
y = 4/7...so when x = 3, y = 4/7.....(3,4/7)
is this for the test on schoolobjects?
The veretx is normally the minimum value
hack:
for f(x)=ax²+bx+c
the x value of the vertex is -b/2a
so
f(x)=1x²-16x+71
x value is -(-16)/(2*1)=16/2=8
find f(8) to find y value of vertex
f(8)=8²-16(8)+71
f(8)=64-128+71
f(8)=7
the vertex is (8,7)
the minimum value is 7
