Question

If the sum of the zeros of a quadratic polynomial 5x^2-kx+6 is 3 then find the value of k

Answer 1

5
$5 \times 9 - 3k + 6 = 0$
$45 - 3k + 6 = 0$
$51 - 3k = 0$
$- 3k = - 51$
$k = - 51 \div - 3$
$k = 17$

Answer 2

${5x}^{2} - kx + 6 = 0 \\ a + b = - b \div a \\ 3 = k \div 5 \\ k = 15$