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If `m` be the slope of common tangent of `y = x^2 - x + 1` and `y = x^2 – 3x + 1`. Then `m` is equal toA. 16B. 7C. 9D. none of these |
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Answer» Correct Answer - B Let y = mx + c be the common tangent to the two parabolas. Then, the equations. `xm+c=x^(2)-3x+10" and "mx+c=x^(2)-x+1` must have equal roots i.e. `x^(2)-x(3+m)+10-c=0" and "x^(2)-x(1+m)=4(1-c)` must have equal roots `:." "(3+m)^(2)=4(10-x)" and "x^(2)-x(1+m)+1-c=0` `rArr" "(3+m)^(2)-(1+m)^(2)=36rArrm=7`. |
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