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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 through 
(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 through (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 through (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. Plug and Simplify Equation: Since the graph of y=g(x)y=g(x) passes through (2,9)(2,9), we plug x=2x=2 and y=9y=9 into the equation g(x)=k2x210kx+6k+1g(x)=k^2x^2-10kx+6k+1. So, 9=k2(2)210k(2)+6k+19=k^2(2)^2-10k(2)+6k+1.
  2. Combine Like Terms: Simplify the equation: 9=4k220k+6k+19=4k^2-20k+6k+1.
  3. Set Equation to Zero: Combine like terms: 9=4k214k+19=4k^2-14k+1.
  4. Factor Quadratic Equation: Subtract 99 from both sides to set the equation to zero: 0=4k214k80=4k^2-14k-8.
  5. Solve for kk: Factor the quadratic equation: (2k+1)(2k8)=0(2k+1)(2k-8)=0.
  6. Find X-Intercepts: Set each factor equal to zero and solve for kk: 2k+1=02k+1=0 or 2k8=02k-8=0.
  7. Substitute kk into g(x)g(x): Solve the first equation: 2k+1=02k+1=0 leads to k=12k=-\frac{1}{2}, which we discard because kk is a positive constant.
  8. Set Equation to Zero: Solve the second equation: 2k8=02k-8=0 leads to k=4k=4.
  9. Simplify Equation: Now we have the value of kk, which is 44. Next, we find the number of xx-intercepts for y=g(x)+5y=-g(x)+5.
  10. Calculate Discriminant: The xx-intercepts occur where y=0y=0. So we set g(x)+5=0-g(x)+5=0.
  11. Calculate Discriminant: The xx-intercepts occur where y=0y=0. So we set g(x)+5=0-g(x)+5=0.Substitute k=4k=4 into g(x)g(x) to get g(x)=42x210(4)x+6(4)+1g(x)=4^2x^2-10(4)x+6(4)+1.
  12. Calculate Discriminant: The xx-intercepts occur where y=0y=0. So we set g(x)+5=0-g(x)+5=0.Substitute k=4k=4 into g(x)g(x) to get g(x)=42x210(4)x+6(4)+1g(x)=4^2x^2-10(4)x+6(4)+1.Simplify g(x)g(x): g(x)=16x240x+25g(x)=16x^2-40x+25.
  13. Calculate Discriminant: The xx-intercepts occur where y=0y=0. So we set g(x)+5=0-g(x)+5=0.Substitute k=4k=4 into g(x)g(x) to get g(x)=42x210(4)x+6(4)+1g(x)=4^2x^2-10(4)x+6(4)+1.Simplify g(x)g(x): g(x)=16x240x+25g(x)=16x^2-40x+25.Now set g(x)+5=0-g(x)+5=0: 16x2+40x25+5=0-16x^2+40x-25+5=0.
  14. Calculate Discriminant: The xx-intercepts occur where y=0y=0. So we set g(x)+5=0-g(x)+5=0.Substitute k=4k=4 into g(x)g(x) to get g(x)=42x210(4)x+6(4)+1g(x)=4^2x^2-10(4)x+6(4)+1.Simplify g(x)g(x): g(x)=16x240x+25g(x)=16x^2-40x+25.Now set g(x)+5=0-g(x)+5=0: 16x2+40x25+5=0-16x^2+40x-25+5=0.Simplify the equation: y=0y=000.
  15. Calculate Discriminant: The xx-intercepts occur where y=0y=0. So we set g(x)+5=0-g(x)+5=0.Substitute k=4k=4 into g(x)g(x) to get g(x)=42x210(4)x+6(4)+1g(x)=4^2x^2-10(4)x+6(4)+1.Simplify g(x)g(x): g(x)=16x240x+25g(x)=16x^2-40x+25.Now set g(x)+5=0-g(x)+5=0: 16x2+40x25+5=0-16x^2+40x-25+5=0.Simplify the equation: y=0y=000.Divide the equation by y=0y=011 to make it simpler: y=0y=022.
  16. Calculate Discriminant: The xx-intercepts occur where y=0y=0. So we set g(x)+5=0-g(x)+5=0.Substitute k=4k=4 into g(x)g(x) to get g(x)=42x210(4)x+6(4)+1g(x)=4^2x^2-10(4)x+6(4)+1.Simplify g(x)g(x): g(x)=16x240x+25g(x)=16x^2-40x+25.Now set g(x)+5=0-g(x)+5=0: 16x2+40x25+5=0-16x^2+40x-25+5=0.Simplify the equation: y=0y=000.Divide the equation by y=0y=011 to make it simpler: y=0y=022.Use the discriminant y=0y=033 to determine the number of xx-intercepts. Here, y=0y=055, y=0y=066, and y=0y=077.
  17. Calculate Discriminant: The xx-intercepts occur where y=0y=0. So we set g(x)+5=0-g(x)+5=0.Substitute k=4k=4 into g(x)g(x) to get g(x)=42x210(4)x+6(4)+1g(x)=4^2x^2-10(4)x+6(4)+1.Simplify g(x)g(x): g(x)=16x240x+25g(x)=16x^2-40x+25.Now set g(x)+5=0-g(x)+5=0: 16x2+40x25+5=0-16x^2+40x-25+5=0.Simplify the equation: y=0y=000.Divide the equation by y=0y=011 to make it simpler: y=0y=022.Use the discriminant y=0y=033 to determine the number of xx-intercepts. Here, y=0y=055, y=0y=066, and y=0y=077.Calculate the discriminant: y=0y=088.
  18. Calculate Discriminant: The xx-intercepts occur where y=0y=0. So we set g(x)+5=0-g(x)+5=0.Substitute k=4k=4 into g(x)g(x) to get g(x)=42x210(4)x+6(4)+1g(x)=4^2x^2-10(4)x+6(4)+1.Simplify g(x)g(x): g(x)=16x240x+25g(x)=16x^2-40x+25.Now set g(x)+5=0-g(x)+5=0: 16x2+40x25+5=0-16x^2+40x-25+5=0.Simplify the equation: y=0y=000.Divide the equation by y=0y=011 to make it simpler: y=0y=022.Use the discriminant y=0y=033 to determine the number of xx-intercepts. Here, y=0y=055, y=0y=066, and y=0y=077.Calculate the discriminant: y=0y=088.Simplify the discriminant: y=0y=099.
  19. Calculate Discriminant: The xx-intercepts occur where y=0y=0. So we set g(x)+5=0-g(x)+5=0.Substitute k=4k=4 into g(x)g(x) to get g(x)=42x210(4)x+6(4)+1g(x)=4^2x^2-10(4)x+6(4)+1.Simplify g(x)g(x): g(x)=16x240x+25g(x)=16x^2-40x+25.Now set g(x)+5=0-g(x)+5=0: 16x2+40x25+5=0-16x^2+40x-25+5=0.Simplify the equation: y=0y=000.Divide the equation by y=0y=011 to make it simpler: y=0y=022.Use the discriminant y=0y=033 to determine the number of xx-intercepts. Here, y=0y=055, y=0y=066, and y=0y=077.Calculate the discriminant: y=0y=088.Simplify the discriminant: y=0y=099.Since the discriminant is greater than g(x)+5=0-g(x)+5=000, there are g(x)+5=0-g(x)+5=011 real and distinct xx-intercepts.

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