silemus.
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  1. 4No solution, linear system
  2. 5Infinite solutions, linear system
  3. 15Probability from a table
  4. 18Median from a frequency table
  5. 22One solution, discriminant=0
  6. 23Max height of a parabola
  7. 25Exponential decay, 15% off
  8. 29Composing f and g
  9. 32Radius from two points
  10. 33Arc length from central angle
  11. 37Similar triangles ratio
  12. 47Two-ticket system of equations
  13. 51No solution, linear equation
  14. 52Taxi cost inequality
  15. 55Scaling 9x-6y+5
  16. 56Costly text message inequality
  17. 59Solving a square root equation
  18. 62Factor theorem on a cubic
  19. 64Percent growth per year
  20. 66x²+y² from sum and product
  21. 67Sum of roots of intersection
  22. 70Completing the square
  23. 73Percent off, then tax
  24. 74Mean with a score removed
  25. 75Overlapping sets, neither
  26. 81Percent of a percent
  27. 82Average speed, unequal times
  28. 85Fraction of a subgroup
  29. 86Mixing to a target percent
  30. 92Inscribed angle theorem
  31. 93Circle from diameter endpoints
  32. 96Sine-cosine complementary angles
  33. 97Area ratio of similar triangles
  34. 98Diagonal of a rectangle
  35. 100Right triangle, tan from cos
  36. 101Volume displaced raises water

70Completing the square

The equation x2−10x+16=(x−h)2−k\displaystyle x^2 - 10x + 16 = (x - h)^2 - k is true for all values of x\displaystyle x, where h\displaystyle h and k\displaystyle k are constants. What is the value of h+k\displaystyle h + k?

The trick is completing the square: rewrite x²−10x+16 as (x−5)²−9, so h=5 and k=9, giving h+k=14. Checking by expanding (x−5)²−9 gives back x²−10x+16.

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