747° Вправа 747Алгебра 8 клас Тарасенкова 2025 · § 18 · стор. 224

747. Знайдіть значення виразу b² – 4ac, якщо:

1) ${\displaystyle a=}$${\displaystyle 1}$, ${\displaystyle b=}$${\displaystyle 4}$, ${\displaystyle c=}$${\displaystyle -5}$:

${\displaystyle b^2-4ac=}$${\displaystyle 4^2-4\cdot 1\cdot (-5)=}$${\displaystyle 16+20=}$${\displaystyle 36}$;

2) ${\displaystyle a=}$${\displaystyle 1}$, ${\displaystyle b=}$${\displaystyle -7}$, ${\displaystyle c=}$${\displaystyle 10}$:

${\displaystyle b^2-4ac=}$${\displaystyle {(-7)}^2-4\cdot 1\cdot 10=}$${\displaystyle 49-40=}$${\displaystyle 9}$;

3) ${\displaystyle a=}$${\displaystyle 5}$, ${\displaystyle b=}$${\displaystyle 6}$, ${\displaystyle c=}$${\displaystyle 1}$:

${\displaystyle b^2-4ac=}$${\displaystyle 6^2-4\cdot 5\cdot 1=}$${\displaystyle 36-20=}$${\displaystyle 16}$;

4) ${\displaystyle a=}$${\displaystyle 3}$, ${\displaystyle b=}$${\displaystyle -5}$, ${\displaystyle c=}$${\displaystyle -2}$:

${\displaystyle b^2-4ac=}$${\displaystyle {(-5)}^2-4\cdot 3\cdot (-2)=}$${\displaystyle 25+24=}$${\displaystyle 49}$.