Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
a)25a2-49b4
=(5a)2-(7b2)2
=(5a-7b2)(5a+7b2)
b)100a2-9b4
=(10a)2-(3b2)2
=(10a-3b2)(10a+3b2)
c)a4-4b2
=(a2)2-(2b)2
=(a2-2b)(a2+2b)
a) 25a2 - 49b2
= (5a + 7b)(5a - 7b)
b) 100a2 - 9b2
= (10a - 3b)(10a + 3b)
c) a4 - 4b2
= (a2 - 2b)(a2 + 2b)
d) \(\dfrac{4}{9}a^{4^{ }}-\dfrac{25}{4}\)
= \(\left(\dfrac{2}{3}a^2+\dfrac{5}{2}\right)\left(\dfrac{2}{3}a^2-\dfrac{5}{2}\right)\)
e) \(\dfrac{1}{4}a^2-b^2\)
=\(\left(\dfrac{1}{2}a-b\right)\left(\dfrac{1}{2}a+b\right)\)
f) \(\dfrac{1}{4}a^2-\dfrac{1}{9}b^2\)
= \(\left(\dfrac{1}{2}a-\dfrac{1}{3}b\right)\left(\dfrac{1}{2}a+\dfrac{1}{3}b\right)\)
g) \(\dfrac{1}{25}-36x^2\)
= \(\left(\dfrac{1}{5}-6x\right)\left(\dfrac{1}{5}+6x\right)\)
h) \(25a^2-\dfrac{1}{4}b^2\)
= \(\left(5a-\dfrac{1}{2}b\right)\left(5a+\dfrac{1}{2}b\right)\)
a. Ta có: a > b
4a > 4b ( nhân cả 2 vế cho 4)
4a - 3 > 4b - 3 (cộng cả 2 vế cho -3)
b. Ta có: a > b
-2a < -2b ( nhân cả 2 vế cho -2)
1 - 2a < 1 - 2b (cộng cả 2 vế cho 1)
d. Ta có: a < b
-2a > -2b ( nhân cả 2 vế cho -2)
5 - 2a > 5 - 2b (cộng cả 2 vế cho 5)
Bài 1:
\(\frac{15ab+5b^2}{9a^2-b^2}=\frac{5b\left(3a+b\right)}{\left(3a\right)^2-b^2}=\frac{5b\left(3a+b\right)}{\left(3a-b\right)\left(3a+b\right)}=\frac{5b}{3a-b}\)
\(\frac{3x^2-3y^2}{9x+9y}=\frac{3\left(x^2-y^2\right)}{9\left(x+y\right)}=\frac{\left(x-y\right)\left(x+y\right)}{3\left(x+y\right)}=\frac{x-y}{3}\)
\(\frac{m^2-4m+4}{2x-4}=\frac{\left(x-2\right)^2}{2\left(x-2\right)}=\frac{x-2}{2}\)
a) \(a^2+2a+1-b^2\)
\(=\left(a+1\right)^2-b^2\)
\(=\left(a+1-b\right)\left(a+1+b\right)\)
b) \(4a^2+4a+1-9b^2\)
\(=\left(2a\right)^2+4a+1-\left(3b\right)^2\)
\(=\left(2a+1\right)^2-\left(3b\right)^2\)
\(=\left(2a+1-3b\right)\left(2a+1+3b\right)\)
Áp dụng bất đẳng thức Cauchy - Schwarz ta có:
\(\left(4a^2+9b^2\right)\left(2^2+2^2\right)\ge\left(2a.1-3b.2\right)^2=\left(4a-6b\right)^2=1\)
\(\Rightarrow4a^2+9b^2\ge\dfrac{1}{8}\).
Đẳng thức xảy ra khi \(a=\dfrac{1}{8};b=\dfrac{-1}{12}\).
다른 사람을 물어보세요! 알았지? 난 대답을 모르겠어요. 정말 미안 해요. 당신에게 좋은 날이 젠장!다른 사람을 물어보세요! 알았지? 난 대답을 모르겠어요. 정말 미안 해요. 당신에게 좋은 날이 젠장!
câu nào mình biết mình trl trc nha:
\(\left(x^2+1\right)^2-4x^2\)
\(=x^4+2x^2+1-4x^2\)
\(=x^4-2x^2+1\)
\(\left(x^2-1\right)^2\)
a. \(9a^2-1=\left(3a-1\right)\left(3a+1\right)\)
\(b.196a^2-4b^2=\left(14a+2b\right)\left(14a-2b\right)\)
\(c.\dfrac{4}{9}a^4-\dfrac{25}{4}=\left(\dfrac{2}{3}a^2-\dfrac{5}{2}\right)\left(\dfrac{2}{3}a^2+\dfrac{5}{2}\right)\)
\(d.\left(a+3b\right)^2-9b^2=\left(a+3b+3b\right)\left(a+3b-3b\right)\\ =\left(a+6b\right)a\)
\(e.81a^2-\left(5a-3b\right)^2=\left(9a-5a+3b\right)\left(9a+5a-3b\right)\\ =\left(4a+3b\right)\left(14a-3b\right)\)
\(f.4\left(2a-b\right)^2-16\left(a-b\right)^2\\ =\left[2\left(2a-b\right)-4\left(a-b\right)\right]\left[2\left(2a-b\right)+4\left(a-b\right)\right]\\ =\left(4a-2b-4a+4b\right)\left(4a-2b+4a-4b\right)\\ =4b\left(5a-3b\right)\)
\(g.x^4-4x^2y+4y^2=\left(x^2-2y\right)^2\)
\(h.9x^6-12x^7+4x^8=x^6\left(9-12x+4x^2\right)\\ =x^6\left(3-2x\right)^2\)