y2-10y+21=0 y=?

Question
Answer:
$$a+b=-10$$ $$ab=1\times 21=21$$
$$-1,-21$$ $$-3,-7$$
$$-1-21=-22$$ $$-3-7=-10$$
$$a=-7$$ $$b=-3$$
$$\left(y^{2}-7y\right)+\left(-3y+21\right)$$
$$y\left(y-7\right)-3\left(y-7\right)$$
$$\left(y-7\right)\left(y-3\right)$$
$$y=7$$ $$y=3$$
solved
general 11 months ago 2746