Answer:

Option 1,3 and 4 are correct.

Step-by-step explanation:

Given is a quadratic equation

x^2-10x+25=0

Marcus used quadratic formula to solve this

The correct use of formula is

frac{-b+/sqrt{b^2-4ac} }{2a}

for the quadratic equation ax^2+bx+c=0

Comparing we have a =1, b =-10: c=25

The student should have substituted -10 for b but he wrong did only 10

II option is wrong since 2 is substituted correctly

III option is right -4ac i.e. the product x 4 must have been subtracted

IV option is right since repeated root is there so only one solution