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Let 
g(x)=k^(2)x^(2)-10 kx+6k+1, where 
k is a positive constant. The graph of 
y=g(x) passes fhrough 
(2,9).
(a) Find 
k.
(b) How many 
x-intercept(s) does the graph of 
y=-g(x)+5 have?

77. Let g(x)=k2x210kx+6k+1 g(x)=k^{2} x^{2}-10 k x+6 k+1 , where k k is a positive constant. The graph of y=g(x) y=g(x) passes fhrough (2,9) (2,9) .\newline(a) Find k k .\newline(b) How many x x -intercept(s) does the graph of y=g(x)+5 y=-g(x)+5 have?

Full solution

Q. 77. Let g(x)=k2x210kx+6k+1 g(x)=k^{2} x^{2}-10 k x+6 k+1 , where k k is a positive constant. The graph of y=g(x) y=g(x) passes fhrough (2,9) (2,9) .\newline(a) Find k k .\newline(b) How many x x -intercept(s) does the graph of y=g(x)+5 y=-g(x)+5 have?
  1. Use Quadratic Formula: Use the quadratic formula to solve for kk.k=(14)±(14)24(4)(8)2(4)k = \frac{-(-14) \pm \sqrt{(-14)^2 - 4(4)(-8)}}{2(4)}k=14±196+1288k = \frac{14 \pm \sqrt{196 + 128}}{8}k=14±3248k = \frac{14 \pm \sqrt{324}}{8}k=14±188k = \frac{14 \pm 18}{8}
  2. Calculate Possible Values: Calculate the two possible values for kk.k=14+188k = \frac{14 + 18}{8} or k=14188k = \frac{14 - 18}{8}k=328k = \frac{32}{8} or k=48k = \frac{-4}{8}k=4k = 4 or k=0.5k = -0.5Since kk is a positive constant, k=4k = 4.
  3. Substitute k=4k = 4: Substitute k=4k = 4 into g(x)g(x) to find the x-intercepts of y=g(x)+5y = -g(x) + 5.
    g(x)=42x210(4)x+6(4)+1g(x) = 4^2x^2 - 10(4)x + 6(4) + 1
    g(x)=16x240x+24+1g(x) = 16x^2 - 40x + 24 + 1
    g(x)=16x240x+25g(x) = 16x^2 - 40x + 25
    y=g(x)+5=16x2+40x25+5y = -g(x) + 5 = -16x^2 + 40x - 25 + 5
    y=16x2+40x20y = -16x^2 + 40x - 20
  4. Determine X-Intercepts: Determine the number of x-intercepts by finding the discriminant of y=16x2+40x20y = -16x^2 + 40x - 20.\newlineDiscriminant, D=b24acD = b^2 - 4ac\newlineD=(40)24(16)(20)D = (40)^2 - 4(-16)(-20)\newlineD=16001280D = 1600 - 1280\newlineD=320D = 320
  5. Discriminant Analysis: Since the discriminant D>0D > 0, there are two distinct real xx-intercepts.

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