Q. 5 Find the values of the constant c for which the line 4y=2x+c is a tangent to th curve y=4x+x8.
Set Equations Equal: To find the values of c for which the line is tangent to the curve, we need to set the two equations equal to each other and find the points of intersection. A tangent line touches the curve at exactly one point, so we are looking for a single solution to the system of equations.
Write Line Equation: First, let's write the equation of the line in slope-intercept form, y=mx+b, where m is the slope and b is the y-intercept. The given line is 4y=2x+c, which can be rewritten as y=21x+4c.
Find Points of Intersection: Now, let's set the equation of the line equal to the equation of the curve to find the points of intersection. We have y=4x+x8 and y=21x+4c. Setting them equal gives us 4x+x8=21x+4c.
Clear Denominator: To solve for x, we need to get rid of the fraction. Multiply every term by x to clear the denominator: x(4x+x8)=x(21x+4c). This simplifies to 4x2+8=21x2+4cx.
Set Equation to Zero: Now, let's move all terms to one side to set the equation to zero: 4x2−(21)x2−(4c)x−8=0. Simplifying the x2 terms gives us (27)x2−(4c)x−8=0.
Discriminant Calculation: This is a quadratic equation in terms of x. For the line to be tangent to the curve, this quadratic equation must have exactly one solution. This means the discriminant of the quadratic equation must be zero. The discriminant is given by b2−4ac, where a, b, and c are the coefficients of the quadratic equation.
Quadratic Equation: In our quadratic equation (27)x2−(4c)x−8=0, a=27, b=−4c, and c=−8. Plugging these into the discriminant formula gives us (−4c)2−4⋅(27)⋅(−8)=0.
Discriminant Formula: Solving for c, we have 16c2−4×(27)×(−8)=0. This simplifies to 16c2+56=0. Multiplying through by 16 to clear the fraction gives us c2+56×16=0.
Solve for c: Now, we solve for c2: c2=−56×16. Since c2 must be a non-negative number, there is no real solution for c. This means there is a math error in our previous steps, as we should expect to find a real value for c.
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