1.

If P(-1,1) is the midpoint of the line segment joining A(-3,b) and B(1, b+4) then b = ? (a) 1 (b) -1 (c) 2 (d) 0

Answer»

Correct answer is (b) -1

The given ports are A(-3,b) and B(1,b + 4).

Then, (x1 = -3,y1 = b) and (x2 = 1,y2 = b + 4)

Therefore,

\(x=\frac{[(-3)+1]}{2}\)

\(\frac{-2}{2}\)

= -1

And

\(y=\frac{[b\,+\,(b\,+\,4)]}{2}\)

\(\frac{2b\,+\,4}{2}\)

= b + 2

But the midpoint is P(-1,1).

Therefore,

b + 2 = 1

\(\Rightarrow b=-1\)



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