Question

$if 3x - 4y = 10 and xy = - 1 find the value of9xsq + 16xsq$
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Answer 1

Answer:

$$\begin{lgathered}\begin{array}{l}{(3 x-4 y)^{2}=10^{2}} \\\\ {(3 x)^{2}+(4 y)^{2}-2.3 x .4 y=100} \\\\ {=9 x^{2}+16 y^{2}-24 x y=100}\end{array}\end{lgathered}$$

Substituting the value of xy from equation 2, we get

$$\begin{lgathered}\begin{array}{l}{=9 x^{2}+16 y^{2}-24(-1)=100} \\\\ {=9 x^{2}+16 y^{2}+24=100} \\\\ {9 x^{2}+16 y^{2}=100-24} \\\\ {9 x^{2}+16 y^{2}=76}\end{array}\end{lgathered}$$

Thus the value of $$9 x^{2}+16 y^{2}$$ is 76

Answer 2

Step-by-step explanation:

(3x-4y)^2=9x^2+16y^2-24xy

100=9x^2+16y^2+24

100-24=9x^2+16y^2

76=9x^2+16y^2

hope this helps you