Đáp án:
a.$9b^2+5ba+\dfrac{25a^2}{36}$
b.$25x^2-10xy+y^2$
c.$4a^2-b^2+10b-25$
d.$x^4-\dfrac4{25}y^2$
Giải thích các bước giải:
a.Ta có:
$(3b+\dfrac{5a}6)^2$
$=(3b)^2+2\cdot 3b\cdot \dfrac{5a}6+(\dfrac{5a}6)^2$
$=9b^2+5ba+\dfrac{25a^2}{36}$
b.Ta có:
$(5x-y)^2$
$=(5x)^2-2\cdot 5x\cdot y+y^2$
$=25x^2-10xy+y^2$
c.Ta có:
$(2a+b-5)(2a-b+5)$
$=(2a+(b-5))(2a-(b-5))$
$=(2a)^2-(b-5)^2$
$=4a^2-(b^2-10b+25)$
$=4a^2-b^2+10b-25$
d.Ta có:
$(x^2+\dfrac25y)(x^2-\dfrac25y)$
$=(x^2)^2-(\dfrac25y)^2$
$=x^4-\dfrac4{25}y^2$
