Multiply the monomial by the binomial and find the value of each for x = −1, y = 0.25 and z = 0.05:
(i) 15y2(2 − 3x)
(ii) −3x(y2 + z2)
(iii) z2(x − y)
(iv) xz(x2 + y2)
(i) To find the product, we will use distributive law as follows:
$15 y^{2}(2-3 x)$
$=15 y^{2} \times 2-15 y^{2} \times 3 x$
$=30 y^{2}-45 x y^{2}$
Substituting $x=-1$ and $y=0.25$ in the result, we get:
$30 y^{2}-45 x y^{2}$
$=30(0.25)^{2}-45(-1)(0.25)^{2}$
$=30 \times 0.0625-\{45 \times(-1) \times 0.0625\}$
$=30 \times 0.0625-\{45 \times(-1) \times 0.0625\}$
$=1.875-(-2.8125)$
$=1.875+2.8125$
$=4.6875$
(ii) To find the product, we will use distributive law as follows:
$-3 x\left(y^{2}+z^{2}\right)$
$=-3 x \times y^{2}+(-3 x) \times z^{2}$
$=-3 x y^{2}-3 x z^{2}$
Substituting $x=-1, y=0.25$ and $z=0.05$ in the result, we get:
$-3 x y^{2}-3 x z^{2}$
$=-3(-1)(0.25)^{2}-3(-1)(0.05)^{2}$
$=-3(-1)(0.0625)-3(-1)(0.0025)$
$=01875+0.0075$
$=0.195$
(iii) To find the product, we will use distributive law as follows:
$z^{2}(x-y)$
$=z^{2} \times x-z^{2} \times y$
$=x z^{2}-y z^{2}$
Substituting $x=-1, y=0.25$ and $z=0.05$ in the result, we get:
$x z^{2}-y z^{2}$
$=(-1)(0.05)^{2}-(0.25)(0.05)^{2}$
$=(-1)(0.0025)-(0.25)(0.0025)$
$=-0.0025-0.000625$
$=-0.003125$
(iv) To find the product, we will use distributive law as follows:
$x z\left(x^{2}+y^{2}\right)$
$=x z \times x^{2}+x z \times y^{2}$
$=x^{3} z+x y^{2} z$
Substituting $x=-1, y=0.25$ and $z=0.05$ in the result, we get:
$x^{3} z+x y^{2} z$
$=(-1)^{3}(0.05)+(-1)(0.25)^{2}(0.05)$
$=(-1)(0.05)+(-1)(0.0625)(0.05)$
$=-0.05-0.003125$
$=-0.053125$