cho x-y=8.Tính B=4x-9/3x+y-4x+9/3y+x vs x khác -3y,y khác -3x 01/10/2021 Bởi Samantha cho x-y=8.Tính B=4x-9/3x+y-4x+9/3y+x vs x khác -3y,y khác -3x
Đáp án: \(\dfrac{{ – 136y – 800}}{{\left( {4y + 24} \right)\left( {4y + 8} \right)}}\) Giải thích các bước giải: \(\begin{array}{l}Do:x – y = 8\\ \to x = y + 8\\Thay:x = y + 8\\ \to B = \dfrac{{4\left( {y + 8} \right) – 9}}{{3\left( {y + 8} \right) + y}} – \dfrac{{4\left( {y + 8} \right) + 9}}{{3y + y + 8}}\\ = \dfrac{{4y + 23}}{{4y + 24}} – \dfrac{{4y + 41}}{{4y + 8}}\\ = \dfrac{{\left( {4y + 23} \right)\left( {4y + 8} \right) – \left( {4y + 41} \right)\left( {4y + 24} \right)}}{{\left( {4y + 24} \right)\left( {4y + 8} \right)}}\\ = \dfrac{{16{y^2} + 124y + 184 – 16{y^2} – 260y – 984}}{{\left( {4y + 24} \right)\left( {4y + 8} \right)}}\\ = \dfrac{{ – 136y – 800}}{{\left( {4y + 24} \right)\left( {4y + 8} \right)}}\end{array}\) Bình luận
Đáp án:
\(\dfrac{{ – 136y – 800}}{{\left( {4y + 24} \right)\left( {4y + 8} \right)}}\)
Giải thích các bước giải:
\(\begin{array}{l}
Do:x – y = 8\\
\to x = y + 8\\
Thay:x = y + 8\\
\to B = \dfrac{{4\left( {y + 8} \right) – 9}}{{3\left( {y + 8} \right) + y}} – \dfrac{{4\left( {y + 8} \right) + 9}}{{3y + y + 8}}\\
= \dfrac{{4y + 23}}{{4y + 24}} – \dfrac{{4y + 41}}{{4y + 8}}\\
= \dfrac{{\left( {4y + 23} \right)\left( {4y + 8} \right) – \left( {4y + 41} \right)\left( {4y + 24} \right)}}{{\left( {4y + 24} \right)\left( {4y + 8} \right)}}\\
= \dfrac{{16{y^2} + 124y + 184 – 16{y^2} – 260y – 984}}{{\left( {4y + 24} \right)\left( {4y + 8} \right)}}\\
= \dfrac{{ – 136y – 800}}{{\left( {4y + 24} \right)\left( {4y + 8} \right)}}
\end{array}\)