Write the quadratic function in the form f(x)=a(x-h)^2+k. then give the vertex of its graph f(x)=x^2-8x+20

At the beginning of 1974/75,2 years a man invested #2000 in a bank at 12.5% compound interest, if it degree #650 at the end of each two years to pay his son's school fees, after payment of interest to pay his son's school fees, how much did he have left at the beginning of the 1978/79 school year?

The difference of two numbers is 40. find the numbers if 0.3 parts of one number is equal to 37.5% of the other one.

In a right triangle δabc, the length of leg ac = 5 ft and the hypotenuse ab = 13 ft. find: b the length of the angle bisector of angle ∠a.