direct variation, and in the equation y=kx the k ca NOT equal 0.
direct variation: y = kx y = kx k = y/x = 0.8/0.4 = 2
Using the discriminant for a quadratic equation the value of k works out as plus or minus 12.
y = kx ie y/x = k, k = 2, so y = 2x
If: kx+y = 4 and y = x^2 +8 Then: x^2 +8 = 4-kx or x^2 +8 -4+kx = 0 => x^2+4+kx = 0 The discriminant of the above quadratic equation must equal 0 So: k^2 -4*(4*1) = 0 => k^2-16 = 0 Therefore: k^2 = 16 and so the values of k are -4 and +4
direct variation, and in the equation y=kx the k ca NOT equal 0.
direct variation: y = kx y = kx k = y/x = 0.8/0.4 = 2
Using the discriminant for a quadratic equation the value of k works out as plus or minus 12.
y = kx ie y/x = k, k = 2, so y = 2x
If: kx+y = 4 and y = x^2 +8 Then: x^2 +8 = 4-kx or x^2 +8 -4+kx = 0 => x^2+4+kx = 0 The discriminant of the above quadratic equation must equal 0 So: k^2 -4*(4*1) = 0 => k^2-16 = 0 Therefore: k^2 = 16 and so the values of k are -4 and +4
Equations: y = kx +1.25 and y^2 = 10x If: y = kx +1.25 then y^2 = (kx +1.25)^2 =>(kx)^2 +2.5kx +1.5625 So: (kx)^2 +2.5kx +1.5625 = 10x Transposing terms: (kx)^2 +2.5kx +1.5625 -10x = 0 Using the discriminant formula: (2.5k -10)^2 -4(1.5625*k^2) Multiplying out the brackets: 6.25k^2 -50k +100 -6.25^2 = 0 Collecting like terms: -50k +100 = 0 Solving the above equation: k = 2 Therefore the value of k is: 2
If the equation is y = kx then the constant of proportionality is k.
an equation of the form y = kx k is the constant of variation
If: y = kx+1 and y = 3x2-4x+4 Then: 3x2-4x+4 = kx+1 So: 3x2-4x-kx+3 = 0 For the line to be tangent to the curve the discriminant of b2-4ac must = 0 So when: -4*3*3 = -36 then (-4-k)2 must = 36 So it follows: (-4-k)(-4-k) = 36 => k2+8k-20 = 0 Solving the quadratic equation: k = 2 or k = -10
By implication : x2-8x+7 = kx-2 Form a quadratic equation: x2-8x-kx+9 = 0 For a line to be a tangent to the curve it must have two equal roots and the discriminant b2-4ac of the quadratic equation must equal 0. So: (-8-k)2-4*1*9 = 0 (-8-k)2-36 = 0 (-8-k)2 = 36 Square root both sides: -8-k = -/+6 -k = 2 or 14 k = -2 or -14 When k = -2 is substituted into the quadratic equation x will have two equal roots of 3 When k = -14 is substituted into the quadratic equation x will have two equal roots of -3
y = kx, where k is a constant, and x and y are the two variables.
y = kx: 10 = 37k so k = 10/37 and y = 10x/37