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Suppose `xa n dy`are real numbers and that `x^2+9y^2-4x+6y+4=0`. Then the maximum value of `((4x-9y))/2`is__________ |
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Answer» `x^(2)+9y^(2)-4x+6y+4=0` or `x^(2)-4y+9y^(2)+6y+4=0` or `(x-2)^(2)+(3y+1)^(2)=1` or `(x-2)^(2)+({y+(1//3)}^(2))/(1//9)=1` which is the equation of the ellipse having center at (2,-1//3). General point on the ellipse is `P(x,y)-=(2+a cos theta, -(1)/(3)+b sin theta)` `-=(2 + cos theta, -(1)/(3)+(1)/(3) sin theta)` `x=2+cos theta and y =-(1)/(3)+(1)/(3) sin theta` `:. 4x-9y=4(2+cos theta)-9(-(1)/(3)+(1)/(3)sin theta)` `or f(theta)=8+4cos theta+3-3 sin theta` `=11+4=16` `:. f(theta)_("max")=11+5=16` |
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