SOLUTION: If a line intersects the x-axis at (a,0) and the y-axis at (0,b) at what point does it intersect the line y=x?

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Question 670835: If a line intersects the x-axis at (a,0) and the y-axis at (0,b) at what point does it intersect the line y=x?

Found 2 solutions by stanbon, josmiceli:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
If a line intersects the x-axis at (a,0) and the y-axis at (0,b) at what point does it intersect the line y=x?
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Equation of the line thru (a,0) and (0,b)
y/b + x/a = 1
y = x
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Solve for x and y:
x/b + x/a = 1
----
ax + bx = ab
(a+b)x = ab
x = (ab)/(a+b)
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Since x = y, the point of intersection is (ab/(a+b) , ab/(a+b))
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Cheers,
Stan H.
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Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
The equation of the line through
(a,0) and (0,b) has slope = +b%2Fa+
and the y-intercept is +b+
The equation is +y+=+%28b%2Fa%29%2Ax+%2B+b+
+y+=+x+
+x+=+%28b%2Fa%29%2Ax+%2B+b+
+%28+1+-+%28b%2Fa%29+%29%2Ax++=+b+
+%28+%28+a+-+b+%29+%2F+a+%29+%2A+x++=+b+
+x+=+%28+a+%2F+%28+a+-+b+%29+%29%2Ab+
+x+=+%28+a%2Ab+%29+%2F+%28+a+-+b+%29+
And, since +y+=+x+, the intersection is at
( (a*b)/( a-b ) , (a*b)/( a-b ) ) answer
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check answer:
Suppose +a+=+3+ , +b+=+7+
+y+=+%28+7%2F3+%29%2Ax++%2B+7+
+y+=+x+
+%287%2F3%29%2Ax+-+x+=+-7+
+%284%2F3%29%2Ax+=+-7+
+x+=+-21%2F4+
and
+x+=+%28+a%2Ab+%29+%2F+%28+a+-+b+%29+
+x+=+21+%2F+%28+3+-+7+%29+
+x+=+-21%2F4+
+y+=+-21%2F4+
OK