Physical purity% of certified soybean seed

For what real value(s) of k does the quadratic equation - x² − (k + 3)x + 2k = 0, have equal real roots?

I. 18p²- 21p + 6 = 0      

II. 16q² - 24q +9 = 0

I. 25p + 2(2p² – 1) = 8(p + 5)

II. 8q² + 35q – 78 = 0

Find the maximum value of f(x)= –2x² +8x + 3.

If x and y satisfy x² + y² = 25 and x + y = 7, find xy.

If α, β are the roots of the equation x² – px + q = 0, then the value of α²+β²+2αβ is 

I. 8/(21x) - 2/7 = 0

II. 16y² - 24y +9 = 0

I. 10x² - 11x + 3 = 0

II. 42y² - 23y – 10 = 0

I. 6x² + 19x + 10 = 0

II. y² + 10y + 25 = 0