0 .. anything times 0 = 0!
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the answer is 8x0/1
The curve y² -2x + 8 = 0 meets the x-axis when y = 0; thus: 0² - 2x + 8 = 0 → 2x = 8 → x = 4. The circle thus passes through the two points (0, 0) and (4, 0); it also has a tangent at y = 2; thus: The chord of the circle between the two points (0, 0) and (4, 0) is parallel to the tangent (at y = 2), thus the x-coordinate of the point when the tangent at y = 2 touches the circle is the midpoint of the chord, namely (4 + 0) / 2 = 2; Thus three points on the circle are (0, 0), (4,0) and (2, 2). The general equation of a circle with centre (x0, y0) and radius r is (x - x0)² + (y - y0)² = r²; thus: As all three points must satisfy this equation: 1) point (0, 0): (0 - x0)² + (y - y0)² = r² → x0² + y0² = r² 2) point (4, 0): (4 - x0)² + (0 - y0)² = r² → 16 - 8x0 + x0² + y0² = r² But from (1) x0² + y0² = r² → 16 - 8x0 + r² = r² → 16 - 8x0 = 0 → 8x0 = 16 → x0 = 2 2) point (2, 2): (2 - x0)² + (2 - y0)² = r² → 4 - 4x0 + x0² + 4 - 4y0 + y0² = r² → 8 - 4x0 - 4y0 + x0² + y0² = r² But from (1) x0² + y0² = r², and from (2) x0 = 2 → 8 - 4 × 2 - 4y0 + r² = r² → 0 - 4y0 = 0 ← y0 = 0 Thus the centre of the circle is at (2, 0); and using (1) the radius (squared) can be found: x0² + y0² = r² → 2² + 0² = r² → r² = 4 Thus the equation of the circle is: (x - 2)² + (y - 0)² = 2² → x² -4x + 4 + y² = 4 → x² + y² - 4x = 0 The above can be shortened by noting that as the tangent at y = 2 is parallel to the chord between the other two points (as both are given to have a y-coordinate of 0), not only is its x-coordinate the mid point of the two points on the chord on the x-axis, that is also the x-coordinate of the centre of the circle as the chord is horizontal, the line from the point where the tangent touches the circle to the centre of the circle is going to be vertical, ie a line of the form x = something.
6x0=0 7x0=0 8x0=0 9x0=0 10x0=0 11x0=0 12x0=0 13x0=0 6x1=6 7x1=7 8x1=8 9x1=9 10x1=10 11x1=11 12x1=12 13x1=13 6x2=12 7x2=14 8x2=16 9x2=18 10x2=20 11x2=22 12x2=24 13x2=26 6x3=18 7x3=21 8x3=24 9x3=27 10x3=30 11x3=33 12x3=36 13x3=39 6x4=24 7x4=28 8x4=32 9x4=36 10x4=40 11x4=44 12x4=48 13x4=52 6x5=30 7x5=35 8x8=40 9x5=45 10x5=50 11x5=55 12x5=60 13x5=65 6x6=36 7x6=42 8x6=48 9x6=54 10x6=60 11x6=66 12x6=72 13x6=78 6x7=42 7x7=49 8x7=56 9x7=63 10x7=70 11x7=77 12x7=84 13x7=91 6x8=48 7x8=56 8x8=64 9x8=72 10x8=80 11x8=88 12x8=96 13x8=104 6x9=54 7x9=63 8x9=72 9x9=81 10x9=90 11x9=99 12x9=108 13x9=117 6x10=60 7x10=70 8x10=80 9x10=90 10x10=100 11x10=110 12x10=120 13x10=130 6x11=66 7x11=77 8x11=88 9x11=99 10x11=110 11x11=121 12x11=132 13x11=143 6x12=72 7x12=84 8x12=96 9x12=108 10x12=120 11x12=132 12x12=144 13x12=156 6x13=78 7x13=91 8x13=104 9x13=117 10x13=130 11x13=143 12x13=156 13x13=169