Ответ:
Обьяснить не могу, только словами у меня в клавиатуре нету деления умножения, а ответ помоему (- 5,6)
<span><span>(<span><span>a2</span>−<span>b2</span>+ab−2</span>)</span><span>(<span><span>a2</span>−<span>b2</span>−ab−2</span>)</span>−<span><span>(<span><span>a2</span>−<span>b2</span>−2</span>)</span>2</span>=</span>Возведение в степень:<span><span>(<span><span>a2</span>−<span>b2</span>+ab−2</span>)</span><span>(<span><span>a2</span>−<span>b2</span>−ab−2</span>)</span>−<span>(<span><span>a4</span>−2<span>a2</span><span>b2</span>−4<span>a2</span>+<span>b4</span>+4<span>b2</span>+4</span>)</span>=</span>Раскрытие скобок:<span><span><span>a4</span>+<span>a2</span><span>(<span>−1</span>)</span><span>b2</span>+<span>a3</span><span>(<span>−1</span>)</span>b+<span>a2</span><span>(<span>−2</span>)</span>−<span>b2</span><span>a2</span>+<span>b4</span>+<span>b3</span>a+2<span>b2</span>+<span>a3</span>b+a<span>b3</span><span>(<span>−1</span>)</span></span><span>+<span>a2</span><span>b2</span><span>(<span>−1</span>)</span>+ab<span>(<span>−2</span>)</span>−2<span>a2</span>+2<span>b2</span>+2ab+4−<span>a4</span>+2<span>a2</span><span>b2</span>+4<span>a2</span>−<span>b4</span>−4<span>b2</span>−4=</span></span><span><span>a2</span><span>(<span>−1</span>)</span><span>b2</span>−<span>b2</span><span>a2</span>+<span>b3</span>a+a<span>b3</span><span>(<span>−1</span>)</span>+<span>a2</span><span>b2</span>=</span><span>−<span>a2</span><span>b2</span>−<span>b2</span><span>a2</span>+<span>b3</span>a−a<span>b3</span>+<span>a2</span><span>b2</span>=</span>−a2b2
(12ⁿ-3ⁿ)/(2ⁿ+1)=3ⁿ*(4ⁿ-1)/(2ⁿ+1)=3ⁿ*(2²ⁿ-1)/(2ⁿ+1)=
=3ⁿ*(2ⁿ+1)*(2ⁿ-1)/(2ⁿ+1)=3ⁿ*(2ⁿ-1).
1) 80% от 20 составит: 20*80/100=16
2) Если обозначим задуманное число х, то составим уравнение:
х+16=70-0,8х
х+0,8х=70-16
1,8х=54
х=54:1,8
х=30
Ответ: задуманное число - 30.
А) ах^2-ау^2=а(х^2-у^2)=а(х-у)(х+у);
б) х^2+10х+25=(х+5)^2=(х+5)(х+5);