How do I solve -3k(k-8)-(k+5)=23?

Answer 1

You have to expland the equation. -3k(k-8) becomes -3k^2 + 24k by multiplying -3k times k and -8. Then we can subtract (k+5) to get -3k^2 - 23k - 5 = 23, or subtracting 23 from each side -3k^2 - 23k - 28 = 0. We can solve this by using the quadratic theorem, k = -b+/-sqrt(b^2 - 4ac)/2a, which can be used to solve any quadratic of the form ax^2 + bx + c = 0. Substituting in, we get k = -23/6 - sqrt(193)/6 and -23/6 + sqrt(193)/6.