(2x4−7x3−6x2+23x−12)÷(x−4)

Each month, a shopkeeper spends 5x + 14 dollars on rent and electricity. if he spends 3x−5 dollars on rent, how much does he spend on electricity? for which value(s) of x is the amount the shopkeeper spends on electricity less than $100? explain how you found the value(s).

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?

What adds to be the bottom number but also multiplies to be the top number with 8 on the bottom and 15 on top