Упр.259 ГДЗ Колягин Ткачёва 7 класс (Алгебра)
- Решить уравнение:
1) $$0{,}71x+1{,}98=0{,}37x-1{,}76$$;
2) $$0{,}18y-7{,}4=0{,}05y-5{,}71$$;
3) $$5(5x-1)-2{,}7x+0{,}2x=6{,}5-0{,}5x$$;
4) $$0{,}36x-0{,}6=0{,}3(0{,}4x-1{,}2)$$. - Упростить выражение:
1) $$(x^2-1)\cdot3x-(x^2-2)\cdot2x$$;
2) $$(4a^2-3b)\cdot2b-(3a^2-4b)\cdot3b$$;
3) $$\frac{2}{3}x(3-6x)+4x(x-1)$$;
4) $$(a-15b)\cdot\frac{4}{5}a-3\left(\frac{1}{5}a^2+2ab\right)$$.
$$0{,}71x+1{,}98=0{,}37x-1{,}76$$
$$0{,}71x-0{,}37x=-1{,}76-1{,}98$$
$$0{,}34x=-3{,}74$$
$$x=\frac{-3{,}74}{0{,}34}=-11$$
$$0{,}18y-7{,}4=0{,}05y-5{,}71$$
$$0{,}18y-0{,}05y=-5{,}71+7{,}4$$
$$0{,}13y=1{,}69$$
$$y=\frac{1{,}69}{0{,}13}=13$$
$$5(5x-1)-2{,}7x+0{,}2x=6{,}5-0{,}5x$$
$$25x-5-2{,}7x+0{,}2x=6{,}5-0{,}5x$$
$$25x-2{,}5x+0{,}2x+0{,}5x=6{,}5+5$$
$$23x=11{,}5$$
$$x=\frac{11{,}5}{23}=0{,}5$$
$$0{,}36x-0{,}6=0{,}3(0{,}4x-1{,}2)$$
$$0{,}36x-0{,}6=0{,}12x-0{,}36$$
$$0{,}36x-0{,}12x=-0{,}36+0{,}6$$
$$0{,}24x=0{,}24$$
$$x=1$$
Ответ
- $$x=-11$$
- $$y=13$$
- $$x=0{,}5$$
- $$x=1$$
$$(x^2-1)\cdot 3x-(x^2-2)\cdot 2x$$
$$=3x^3-3x-2x^3+4x$$
$$=x^3+x$$
$$(4a^2-3b)\cdot 2b-(3a^2-4b)\cdot 3b$$
$$=8a^2b-6b^2-9a^2b+12b^2$$
$$=6b^2-a^2b$$
$$\frac{2}{3}x(3-6x)+4x(x-1)$$
$$=2x-4x^2+4x^2-4x$$
$$=-2x$$
$$(a-15b)\cdot \frac{4}{5}a-3\left(\frac{1}{5}a^2+2ab\right)$$
$$=\frac{4}{5}a^2-12ab-\frac{3}{5}a^2-6ab$$
$$=\frac{1}{5}a^2-18ab$$
Ответ
- $$x^3+x$$
- $$6b^2-a^2b$$
- $$-2x$$
- $$\frac{1}{5}a^2-18ab$$
