а)f(x)=x<span>²-7x+12</span>
<span>x</span><span>²-7x+12=0</span>
<span>x=3 x=4</span>
<span>б)f(x)=3x</span><span>²-2x-5</span>
<span>3x</span><span>²-2x-5=0</span>
<span>Д=(-2)</span><span>²-4*3*(-5)=4-60=-56</span>
<span><span>д<0</span></span>
<span><span>розв'язку немає</span></span>
<span><span>
</span></span>
<span><span>інших немаю часу вирішити....</span></span>